Lib/pydoc.py

#!/usr/bin/env python
# -*- coding: latin-1 -*-
"""Generate Python documentation in HTML or text for interactive use.

In the Python interpreter, do "from pydoc import help" to provide online
help.  Calling help(thing) on a Python object documents the object.

Or, at the shell command line outside of Python:

Run "pydoc <name>" to show documentation on something.  <name> may be
the name of a function, module, package, or a dotted reference to a
class or function within a module or module in a package.  If the
argument contains a path segment delimiter (e.g. slash on Unix,
backslash on Windows) it is treated as the path to a Python source file.

Run "pydoc -k <keyword>" to search for a keyword in the synopsis lines
of all available modules.

Run "pydoc -p <port>" to start an HTTP server on a given port on the
local machine to generate documentation web pages.

For platforms without a command line, "pydoc -g" starts the HTTP server
and also pops up a little window for controlling it.

Run "pydoc -w <name>" to write out the HTML documentation for a module
to a file named "<name>.html".

Module docs for core modules are assumed to be in

    http://docs.python.org/library/

This can be overridden by setting the PYTHONDOCS environment variable
to a different URL or to a local directory containing the Library
Reference Manual pages.
"""

__author__ = "Ka-Ping Yee <ping@lfw.org>"
__date__ = "26 February 2001"

__version__ = "$Revision$"
__credits__ = """Guido van Rossum, for an excellent programming language.
Tommy Burnette, the original creator of manpy.
Paul Prescod, for all his work on onlinehelp.
Richard Chamberlain, for the first implementation of textdoc.
"""

# Known bugs that can't be fixed here:
#   - imp.load_module() cannot be prevented from clobbering existing
#     loaded modules, so calling synopsis() on a binary module file
#     changes the contents of any existing module with the same name.
#   - If the __file__ attribute on a module is a relative path and
#     the current directory is changed with os.chdir(), an incorrect
#     path will be displayed.

import sys, imp, os, re, inspect, builtins, pkgutil
from reprlib import Repr
try:
    from collections import deque
except ImportError:
    # Python 2.3 compatibility
    class deque(list):
        def popleft(self):
            return self.pop(0)

# --------------------------------------------------------- common routines

def pathdirs():
    """Convert sys.path into a list of absolute, existing, unique paths."""
    dirs = []
    normdirs = []
    for dir in sys.path:
        dir = os.path.abspath(dir or '.')
        normdir = os.path.normcase(dir)
        if normdir not in normdirs and os.path.isdir(dir):
            dirs.append(dir)
            normdirs.append(normdir)
    return dirs

def getdoc(object):
    """Get the doc string or comments for an object."""
    result = inspect.getdoc(object) or inspect.getcomments(object)
    return result and re.sub('^ *\n', '', result.rstrip()) or ''

def splitdoc(doc):
    """Split a doc string into a synopsis line (if any) and the rest."""
    lines = doc.strip().split('\n')
    if len(lines) == 1:
        return lines[0], ''
    elif len(lines) >= 2 and not lines[1].rstrip():
        return lines[0], '\n'.join(lines[2:])
    return '', '\n'.join(lines)

def classname(object, modname):
    """Get a class name and qualify it with a module name if necessary."""
    name = object.__name__
    if object.__module__ != modname:
        name = object.__module__ + '.' + name
    return name

def isdata(object):
    """Check if an object is of a type that probably means it's data."""
    return not (inspect.ismodule(object) or inspect.isclass(object) or
                inspect.isroutine(object) or inspect.isframe(object) or
                inspect.istraceback(object) or inspect.iscode(object))

def replace(text, *pairs):
    """Do a series of global replacements on a string."""
    while pairs:
        text = pairs[1].join(text.split(pairs[0]))
        pairs = pairs[2:]
    return text

def cram(text, maxlen):
    """Omit part of a string if needed to make it fit in a maximum length."""
    if len(text) > maxlen:
        pre = max(0, (maxlen-3)//2)
        post = max(0, maxlen-3-pre)
        return text[:pre] + '...' + text[len(text)-post:]
    return text

_re_stripid = re.compile(r' at 0x[0-9a-f]{6,16}(>+)$', re.IGNORECASE)
def stripid(text):
    """Remove the hexadecimal id from a Python object representation."""
    # The behaviour of %p is implementation-dependent in terms of case.
    if _re_stripid.search(repr(Exception)):
        return _re_stripid.sub(r'\1', text)
    return text

def _is_some_method(obj):
    return inspect.ismethod(obj) or inspect.ismethoddescriptor(obj)

def allmethods(cl):
    methods = {}
    for key, value in inspect.getmembers(cl, _is_some_method):
        methods[key] = 1
    for base in cl.__bases__:
        methods.update(allmethods(base)) # all your base are belong to us
    for key in methods.keys():
        methods[key] = getattr(cl, key)
    return methods

def _split_list(s, predicate):
    """Split sequence s via predicate, and return pair ([true], [false]).

    The return value is a 2-tuple of lists,
        ([x for x in s if predicate(x)],
         [x for x in s if not predicate(x)])
    """

    yes = []
    no = []
    for x in s:
        if predicate(x):
            yes.append(x)
        else:
            no.append(x)
    return yes, no

def visiblename(name, all=None):
    """Decide whether to show documentation on a variable."""
    # Certain special names are redundant.
    _hidden_names = ('__builtins__', '__doc__', '__file__', '__path__',
                     '__module__', '__name__', '__slots__', '__package__')
    if name in _hidden_names: return 0
    # Private names are hidden, but special names are displayed.
    if name.startswith('__') and name.endswith('__'): return 1
    if all is not None:
        # only document that which the programmer exported in __all__
        return name in all
    else:
        return not name.startswith('_')

def classify_class_attrs(object):
    """Wrap inspect.classify_class_attrs, with fixup for data descriptors."""
    results = []
    for (name, kind, cls, value) in inspect.classify_class_attrs(object):
        if inspect.isdatadescriptor(value):
            kind = 'data descriptor'
        results.append((name, kind, cls, value))
    return results

# ----------------------------------------------------- module manipulation

def ispackage(path):
    """Guess whether a path refers to a package directory."""
    if os.path.isdir(path):
        for ext in ('.py', '.pyc', '.pyo'):
            if os.path.isfile(os.path.join(path, '__init__' + ext)):
                return True
    return False

def source_synopsis(file):
    line = file.readline()
    while line[:1] == '#' or not line.strip():
        line = file.readline()
        if not line: break
    line = line.strip()
    if line[:4] == 'r"""': line = line[1:]
    if line[:3] == '"""':
        line = line[3:]
        if line[-1:] == '\\': line = line[:-1]
        while not line.strip():
            line = file.readline()
            if not line: break
        result = line.split('"""')[0].strip()
    else: result = None
    return result

def synopsis(filename, cache={}):
    """Get the one-line summary out of a module file."""
    mtime = os.stat(filename).st_mtime
    lastupdate, result = cache.get(filename, (0, None))
    if lastupdate < mtime:
        info = inspect.getmoduleinfo(filename)
        try:
            file = open(filename)
        except IOError:
            # module can't be opened, so skip it
            return None
        if info and 'b' in info[2]: # binary modules have to be imported
            try: module = imp.load_module('__temp__', file, filename, info[1:])
            except: return None
            result = (module.__doc__ or '').splitlines()[0]
            del sys.modules['__temp__']
        else: # text modules can be directly examined
            result = source_synopsis(file)
            file.close()
        cache[filename] = (mtime, result)
    return result

class ErrorDuringImport(Exception):
    """Errors that occurred while trying to import something to document it."""
    def __init__(self, filename, exc_info):
        self.filename = filename
        self.exc, self.value, self.tb = exc_info

    def __str__(self):
        exc = self.exc.__name__
        return 'problem in %s - %s: %s' % (self.filename, exc, self.value)

def importfile(path):
    """Import a Python source file or compiled file given its path."""
    magic = imp.get_magic()
    file = open(path, 'r')
    if file.read(len(magic)) == magic:
        kind = imp.PY_COMPILED
    else:
        kind = imp.PY_SOURCE
    file.close()
    filename = os.path.basename(path)
    name, ext = os.path.splitext(filename)
    file = open(path, 'r')
    try:
        module = imp.load_module(name, file, path, (ext, 'r', kind))
    except:
        raise ErrorDuringImport(path, sys.exc_info())
    file.close()
    return module

def safeimport(path, forceload=0, cache={}):
    """Import a module; handle errors; return None if the module isn't found.

    If the module *is* found but an exception occurs, it's wrapped in an
    ErrorDuringImport exception and reraised.  Unlike __import__, if a
    package path is specified, the module at the end of the path is returned,
    not the package at the beginning.  If the optional 'forceload' argument
    is 1, we reload the module from disk (unless it's a dynamic extension)."""
    try:
        # If forceload is 1 and the module has been previously loaded from
        # disk, we always have to reload the module.  Checking the file's
        # mtime isn't good enough (e.g. the module could contain a class
        # that inherits from another module that has changed).
        if forceload and path in sys.modules:
            if path not in sys.builtin_module_names:
                # Remove the module from sys.modules and re-import to try
                # and avoid problems with partially loaded modules.
                # Also remove any submodules because they won't appear
                # in the newly loaded module's namespace if they're already
                # in sys.modules.
                subs = [m for m in sys.modules if m.startswith(path + '.')]
                for key in [path] + subs:
                    # Prevent garbage collection.
                    cache[key] = sys.modules[key]
                    del sys.modules[key]
        module = __import__(path)
    except:
        # Did the error occur before or after the module was found?
        (exc, value, tb) = info = sys.exc_info()
        if path in sys.modules:
            # An error occurred while executing the imported module.
            raise ErrorDuringImport(sys.modules[path].__file__, info)
        elif exc is SyntaxError:
            # A SyntaxError occurred before we could execute the module.
            raise ErrorDuringImport(value.filename, info)
        elif exc is ImportError and \
             str(value).lower().split()[:2] == ['no', 'module']:
            # The module was not found.
            return None
        else:
            # Some other error occurred during the importing process.
            raise ErrorDuringImport(path, sys.exc_info())
    for part in path.split('.')[1:]:
        try: module = getattr(module, part)
        except AttributeError: return None
    return module

# ---------------------------------------------------- formatter base class

class Doc:
    def document(self, object, name=None, *args):
        """Generate documentation for an object."""
        args = (object, name) + args
        # 'try' clause is to attempt to handle the possibility that inspect
        # identifies something in a way that pydoc itself has issues handling;
        # think 'super' and how it is a descriptor (which raises the exception
        # by lacking a __name__ attribute) and an instance.
        if inspect.isgetsetdescriptor(object): return self.docdata(*args)
        if inspect.ismemberdescriptor(object): return self.docdata(*args)
        try:
            if inspect.ismodule(object): return self.docmodule(*args)
            if inspect.isclass(object): return self.docclass(*args)
            if inspect.isroutine(object): return self.docroutine(*args)
        except AttributeError:
            pass
        if isinstance(object, property): return self.docproperty(*args)
        return self.docother(*args)

    def fail(self, object, name=None, *args):
        """Raise an exception for unimplemented types."""
        message = "don't know how to document object%s of type %s" % (
            name and ' ' + repr(name), type(object).__name__)
        raise TypeError(message)

    docmodule = docclass = docroutine = docother = docproperty = docdata = fail

    def getdocloc(self, object):
        """Return the location of module docs or None"""

        try:
            file = inspect.getabsfile(object)
        except TypeError:
            file = '(built-in)'

        docloc = os.environ.get("PYTHONDOCS",
                                "http://docs.python.org/library")
        basedir = os.path.join(sys.exec_prefix, "lib",
                               "python"+sys.version[0:3])
        if (isinstance(object, type(os)) and
            (object.__name__ in ('errno', 'exceptions', 'gc', 'imp',
                                 'marshal', 'posix', 'signal', 'sys',
                                 '_thread', 'zipimport') or
             (file.startswith(basedir) and
              not file.startswith(os.path.join(basedir, 'site-packages'))))):
            if docloc.startswith("http://"):
                docloc = "%s/%s" % (docloc.rstrip("/"), object.__name__)
            else:
                docloc = os.path.join(docloc, object.__name__ + ".html")
        else:
            docloc = None
        return docloc

# -------------------------------------------- HTML documentation generator

class HTMLRepr(Repr):
    """Class for safely making an HTML representation of a Python object."""
    def __init__(self):
        Repr.__init__(self)
        self.maxlist = self.maxtuple = 20
        self.maxdict = 10
        self.maxstring = self.maxother = 100

    def escape(self, text):
        return replace(text, '&', '&amp;', '<', '&lt;', '>', '&gt;')

    def repr(self, object):
        return Repr.repr(self, object)

    def repr1(self, x, level):
        if hasattr(type(x), '__name__'):
            methodname = 'repr_' + '_'.join(type(x).__name__.split())
            if hasattr(self, methodname):
                return getattr(self, methodname)(x, level)
        return self.escape(cram(stripid(repr(x)), self.maxother))

    def repr_string(self, x, level):
        test = cram(x, self.maxstring)
        testrepr = repr(test)
        if '\\' in test and '\\' not in replace(testrepr, r'\\', ''):
            # Backslashes are only literal in the string and are never
            # needed to make any special characters, so show a raw string.
            return 'r' + testrepr[0] + self.escape(test) + testrepr[0]
        return re.sub(r'((\\[\\abfnrtv\'"]|\\[0-9]..|\\x..|\\u....)+)',
                      r'<font color="#c040c0">\1</font>',
                      self.escape(testrepr))

    repr_str = repr_string

    def repr_instance(self, x, level):
        try:
            return self.escape(cram(stripid(repr(x)), self.maxstring))
        except:
            return self.escape('<%s instance>' % x.__class__.__name__)

    repr_unicode = repr_string

class HTMLDoc(Doc):
    """Formatter class for HTML documentation."""

    # ------------------------------------------- HTML formatting utilities

    _repr_instance = HTMLRepr()
    repr = _repr_instance.repr
    escape = _repr_instance.escape

    def page(self, title, contents):
        """Format an HTML page."""
        return '''
<!doctype html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html><head><title>Python: %s</title>
</head><body bgcolor="#f0f0f8">
%s
</body></html>''' % (title, contents)

    def heading(self, title, fgcol, bgcol, extras=''):
        """Format a page heading."""
        return '''
<table width="100%%" cellspacing=0 cellpadding=2 border=0 summary="heading">
<tr bgcolor="%s">
<td valign=bottom>&nbsp;<br>
<font color="%s" face="helvetica, arial">&nbsp;<br>%s</font></td
><td align=right valign=bottom
><font color="%s" face="helvetica, arial">%s</font></td></tr></table>
    ''' % (bgcol, fgcol, title, fgcol, extras or '&nbsp;')

    def section(self, title, fgcol, bgcol, contents, width=6,
                prelude='', marginalia=None, gap='&nbsp;'):
        """Format a section with a heading."""
        if marginalia is None:
            marginalia = '<tt>' + '&nbsp;' * width + '</tt>'
        result = '''<p>
<table width="100%%" cellspacing=0 cellpadding=2 border=0 summary="section">
<tr bgcolor="%s">
<td colspan=3 valign=bottom>&nbsp;<br>
<font color="%s" face="helvetica, arial">%s</font></td></tr>
    ''' % (bgcol, fgcol, title)
        if prelude:
            result = result + '''
<tr bgcolor="%s"><td rowspan=2>%s</td>
<td colspan=2>%s</td></tr>
<tr><td>%s</td>''' % (bgcol, marginalia, prelude, gap)
        else:
            result = result + '''
<tr><td bgcolor="%s">%s</td><td>%s</td>''' % (bgcol, marginalia, gap)

        return result + '\n<td width="100%%">%s</td></tr></table>' % contents

    def bigsection(self, title, *args):
        """Format a section with a big heading."""
        title = '<big><strong>%s</strong></big>' % title
        return self.section(title, *args)

    def preformat(self, text):
        """Format literal preformatted text."""
        text = self.escape(text.expandtabs())
        return replace(text, '\n\n', '\n \n', '\n\n', '\n \n',
                             ' ', '&nbsp;', '\n', '<br>\n')

    def multicolumn(self, list, format, cols=4):
        """Format a list of items into a multi-column list."""
        result = ''
        rows = (len(list)+cols-1)//cols
        for col in range(cols):
            result = result + '<td width="%d%%" valign=top>' % (100//cols)
            for i in range(rows*col, rows*col+rows):
                if i < len(list):
                    result = result + format(list[i]) + '<br>\n'
            result = result + '</td>'
        return '<table width="100%%" summary="list"><tr>%s</tr></table>' % result

    def grey(self, text): return '<font color="#909090">%s</font>' % text

    def namelink(self, name, *dicts):
        """Make a link for an identifier, given name-to-URL mappings."""
        for dict in dicts:
            if name in dict:
                return '<a href="%s">%s</a>' % (dict[name], name)
        return name

    def classlink(self, object, modname):
        """Make a link for a class."""
        name, module = object.__name__, sys.modules.get(object.__module__)
        if hasattr(module, name) and getattr(module, name) is object:
            return '<a href="%s.html#%s">%s</a>' % (
                module.__name__, name, classname(object, modname))
        return classname(object, modname)

    def modulelink(self, object):
        """Make a link for a module."""
        return '<a href="%s.html">%s</a>' % (object.__name__, object.__name__)

    def modpkglink(self, modpkginfo):
        """Make a link for a module or package to display in an index."""
        name, path, ispackage, shadowed = modpkginfo
        if shadowed:
            return self.grey(name)
        if path:
            url = '%s.%s.html' % (path, name)
        else:
            url = '%s.html' % name
        if ispackage:
            text = '<strong>%s</strong>&nbsp;(package)' % name
        else:
            text = name
        return '<a href="%s">%s</a>' % (url, text)

    def markup(self, text, escape=None, funcs={}, classes={}, methods={}):
        """Mark up some plain text, given a context of symbols to look for.
        Each context dictionary maps object names to anchor names."""
        escape = escape or self.escape
        results = []
        here = 0
        pattern = re.compile(r'\b((http|ftp)://\S+[\w/]|'
                                r'RFC[- ]?(\d+)|'
                                r'PEP[- ]?(\d+)|'
                                r'(self\.)?(\w+))')
        while True:
            match = pattern.search(text, here)
            if not match: break
            start, end = match.span()
            results.append(escape(text[here:start]))

            all, scheme, rfc, pep, selfdot, name = match.groups()
            if scheme:
                url = escape(all).replace('"', '&quot;')
                results.append('<a href="%s">%s</a>' % (url, url))
            elif rfc:
                url = 'http://www.rfc-editor.org/rfc/rfc%d.txt' % int(rfc)
                results.append('<a href="%s">%s</a>' % (url, escape(all)))
            elif pep:
                url = 'http://www.python.org/dev/peps/pep-%04d/' % int(pep)
                results.append('<a href="%s">%s</a>' % (url, escape(all)))
            elif text[end:end+1] == '(':
                results.append(self.namelink(name, methods, funcs, classes))
            elif selfdot:
                results.append('self.<strong>%s</strong>' % name)
            else:
                results.append(self.namelink(name, classes))
            here = end
        results.append(escape(text[here:]))
        return ''.join(results)

    # ---------------------------------------------- type-specific routines

    def formattree(self, tree, modname, parent=None):
        """Produce HTML for a class tree as given by inspect.getclasstree()."""
        result = ''
        for entry in tree:
            if type(entry) is type(()):
                c, bases = entry
                result = result + '<dt><font face="helvetica, arial">'
                result = result + self.classlink(c, modname)
                if bases and bases != (parent,):
                    parents = []
                    for base in bases:
                        parents.append(self.classlink(base, modname))
                    result = result + '(' + ', '.join(parents) + ')'
                result = result + '\n</font></dt>'
            elif type(entry) is type([]):
                result = result + '<dd>\n%s</dd>\n' % self.formattree(
                    entry, modname, c)
        return '<dl>\n%s</dl>\n' % result

    def docmodule(self, object, name=None, mod=None, *ignored):
        """Produce HTML documentation for a module object."""
        name = object.__name__ # ignore the passed-in name
        try:
            all = object.__all__
        except AttributeError:
            all = None
        parts = name.split('.')
        links = []
        for i in range(len(parts)-1):
            links.append(
                '<a href="%s.html"><font color="#ffffff">%s</font></a>' %
                ('.'.join(parts[:i+1]), parts[i]))
        linkedname = '.'.join(links + parts[-1:])
        head = '<big><big><strong>%s</strong></big></big>' % linkedname
        try:
            path = inspect.getabsfile(object)
            url = path
            if sys.platform == 'win32':
                import nturl2path
                url = nturl2path.pathname2url(path)
            filelink = '<a href="file:%s">%s</a>' % (url, path)
        except TypeError:
            filelink = '(built-in)'
        info = []
        if hasattr(object, '__version__'):
            version = str(object.__version__)
            if version[:11] == '$' + 'Revision: ' and version[-1:] == '$':
                version = version[11:-1].strip()
            info.append('version %s' % self.escape(version))
        if hasattr(object, '__date__'):
            info.append(self.escape(str(object.__date__)))
        if info:
            head = head + ' (%s)' % ', '.join(info)
        docloc = self.getdocloc(object)
        if docloc is not None:
            docloc = '<br><a href="%(docloc)s">Module Docs</a>' % locals()
        else:
            docloc = ''
        result = self.heading(
            head, '#ffffff', '#7799ee',
            '<a href=".">index</a><br>' + filelink + docloc)

        modules = inspect.getmembers(object, inspect.ismodule)

        classes, cdict = [], {}
        for key, value in inspect.getmembers(object, inspect.isclass):
            # if __all__ exists, believe it.  Otherwise use old heuristic.
            if (all is not None or
                (inspect.getmodule(value) or object) is object):
                if visiblename(key, all):
                    classes.append((key, value))
                    cdict[key] = cdict[value] = '#' + key
        for key, value in classes:
            for base in value.__bases__:
                key, modname = base.__name__, base.__module__
                module = sys.modules.get(modname)
                if modname != name and module and hasattr(module, key):
                    if getattr(module, key) is base:
                        if not key in cdict:
                            cdict[key] = cdict[base] = modname + '.html#' + key
        funcs, fdict = [], {}
        for key, value in inspect.getmembers(object, inspect.isroutine):
            # if __all__ exists, believe it.  Otherwise use old heuristic.
            if (all is not None or
                inspect.isbuiltin(value) or inspect.getmodule(value) is object):
                if visiblename(key, all):
                    funcs.append((key, value))
                    fdict[key] = '#-' + key
                    if inspect.isfunction(value): fdict[value] = fdict[key]
        data = []
        for key, value in inspect.getmembers(object, isdata):
            if visiblename(key, all):
                data.append((key, value))

        doc = self.markup(getdoc(object), self.preformat, fdict, cdict)
        doc = doc and '<tt>%s</tt>' % doc
        result = result + '<p>%s</p>\n' % doc

        if hasattr(object, '__path__'):
            modpkgs = []
            for importer, modname, ispkg in pkgutil.iter_modules(object.__path__):
                modpkgs.append((modname, name, ispkg, 0))
            modpkgs.sort()
            contents = self.multicolumn(modpkgs, self.modpkglink)
            result = result + self.bigsection(
                'Package Contents', '#ffffff', '#aa55cc', contents)
        elif modules:
            contents = self.multicolumn(
                modules, lambda t: self.modulelink(t[1]))
            result = result + self.bigsection(
                'Modules', '#ffffff', '#aa55cc', contents)

        if classes:
            classlist = [value for (key, value) in classes]
            contents = [
                self.formattree(inspect.getclasstree(classlist, 1), name)]
            for key, value in classes:
                contents.append(self.document(value, key, name, fdict, cdict))
            result = result + self.bigsection(
                'Classes', '#ffffff', '#ee77aa', ' '.join(contents))
        if funcs:
            contents = []
            for key, value in funcs:
                contents.append(self.document(value, key, name, fdict, cdict))
            result = result + self.bigsection(
                'Functions', '#ffffff', '#eeaa77', ' '.join(contents))
        if data:
            contents = []
            for key, value in data:
                contents.append(self.document(value, key))
            result = result + self.bigsection(
                'Data', '#ffffff', '#55aa55', '<br>\n'.join(contents))
        if hasattr(object, '__author__'):
            contents = self.markup(str(object.__author__), self.preformat)
            result = result + self.bigsection(
                'Author', '#ffffff', '#7799ee', contents)
        if hasattr(object, '__credits__'):
            contents = self.markup(str(object.__credits__), self.preformat)
            result = result + self.bigsection(
                'Credits', '#ffffff', '#7799ee', contents)

        return result

    def docclass(self, object, name=None, mod=None, funcs={}, classes={},
                 *ignored):
        """Produce HTML documentation for a class object."""
        realname = object.__name__
        name = name or realname
        bases = object.__bases__

        contents = []
        push = contents.append

        # Cute little class to pump out a horizontal rule between sections.
        class HorizontalRule:
            def __init__(self):
                self.needone = 0
            def maybe(self):
                if self.needone:
                    push('<hr>\n')
                self.needone = 1
        hr = HorizontalRule()

        # List the mro, if non-trivial.
        mro = deque(inspect.getmro(object))
        if len(mro) > 2:
            hr.maybe()
            push('<dl><dt>Method resolution order:</dt>\n')
            for base in mro:
                push('<dd>%s</dd>\n' % self.classlink(base,
                                                      object.__module__))
            push('</dl>\n')

        def spill(msg, attrs, predicate):
            ok, attrs = _split_list(attrs, predicate)
            if ok:
                hr.maybe()
                push(msg)
                for name, kind, homecls, value in ok:
                    push(self.document(getattr(object, name), name, mod,
                                       funcs, classes, mdict, object))
                    push('\n')
            return attrs

        def spilldescriptors(msg, attrs, predicate):
            ok, attrs = _split_list(attrs, predicate)
            if ok:
                hr.maybe()
                push(msg)
                for name, kind, homecls, value in ok:
                    push(self._docdescriptor(name, value, mod))
            return attrs

        def spilldata(msg, attrs, predicate):
            ok, attrs = _split_list(attrs, predicate)
            if ok:
                hr.maybe()
                push(msg)
                for name, kind, homecls, value in ok:
                    base = self.docother(getattr(object, name), name, mod)
                    if hasattr(value, '__call__') or inspect.isdatadescriptor(value):
                        doc = getattr(value, "__doc__", None)
                    else:
                        doc = None
                    if doc is None:
                        push('<dl><dt>%s</dl>\n' % base)
                    else:
                        doc = self.markup(getdoc(value), self.preformat,
                                          funcs, classes, mdict)
                        doc = '<dd><tt>%s</tt>' % doc
                        push('<dl><dt>%s%s</dl>\n' % (base, doc))
                    push('\n')
            return attrs

        attrs = [(name, kind, cls, value)
                 for name, kind, cls, value in classify_class_attrs(object)
                 if visiblename(name)]

        mdict = {}
        for key, kind, homecls, value in attrs:
            mdict[key] = anchor = '#' + name + '-' + key
            value = getattr(object, key)
            try:
                # The value may not be hashable (e.g., a data attr with
                # a dict or list value).
                mdict[value] = anchor
            except TypeError:
                pass

        while attrs:
            if mro:
                thisclass = mro.popleft()
            else:
                thisclass = attrs[0][2]
            attrs, inherited = _split_list(attrs, lambda t: t[2] is thisclass)

            if thisclass is builtins.object:
                attrs = inherited
                continue
            elif thisclass is object:
                tag = 'defined here'
            else:
                tag = 'inherited from %s' % self.classlink(thisclass,
                                                           object.__module__)
            tag += ':<br>\n'

            # Sort attrs by name.
            attrs.sort(key=lambda t: t[0])

            # Pump out the attrs, segregated by kind.
            attrs = spill('Methods %s' % tag, attrs,
                          lambda t: t[1] == 'method')
            attrs = spill('Class methods %s' % tag, attrs,
                          lambda t: t[1] == 'class method')
            attrs = spill('Static methods %s' % tag, attrs,
                          lambda t: t[1] == 'static method')
            attrs = spilldescriptors('Data descriptors %s' % tag, attrs,
                                     lambda t: t[1] == 'data descriptor')
            attrs = spilldata('Data and other attributes %s' % tag, attrs,
                              lambda t: t[1] == 'data')
            assert attrs == []
            attrs = inherited

        contents = ''.join(contents)

        if name == realname:
            title = '<a name="%s">class <strong>%s</strong></a>' % (
                name, realname)
        else:
            title = '<strong>%s</strong> = <a name="%s">class %s</a>' % (
                name, name, realname)
        if bases:
            parents = []
            for base in bases:
                parents.append(self.classlink(base, object.__module__))
            title = title + '(%s)' % ', '.join(parents)
        doc = self.markup(getdoc(object), self.preformat, funcs, classes, mdict)
        doc = doc and '<tt>%s<br>&nbsp;</tt>' % doc

        return self.section(title, '#000000', '#ffc8d8', contents, 3, doc)

    def formatvalue(self, object):
        """Format an argument default value as text."""
        return self.grey('=' + self.repr(object))

    def docroutine(self, object, name=None, mod=None,
                   funcs={}, classes={}, methods={}, cl=None):
        """Produce HTML documentation for a function or method object."""
        realname = object.__name__
        name = name or realname
        anchor = (cl and cl.__name__ or '') + '-' + name
        note = ''
        skipdocs = 0
        if inspect.ismethod(object):
            imclass = object.__self__.__class__
            if cl:
                if imclass is not cl:
                    note = ' from ' + self.classlink(imclass, mod)
            else:
                if object.__self__ is not None:
                    note = ' method of %s instance' % self.classlink(
                        object.__self__.__class__, mod)
                else:
                    note = ' unbound %s method' % self.classlink(imclass,mod)
            object = object.__func__

        if name == realname:
            title = '<a name="%s"><strong>%s</strong></a>' % (anchor, realname)
        else:
            if (cl and realname in cl.__dict__ and
                cl.__dict__[realname] is object):
                reallink = '<a href="#%s">%s</a>' % (
                    cl.__name__ + '-' + realname, realname)
                skipdocs = 1
            else:
                reallink = realname
            title = '<a name="%s"><strong>%s</strong></a> = %s' % (
                anchor, name, reallink)
        if inspect.isfunction(object):
            args, varargs, kwonlyargs, kwdefaults, varkw, defaults, ann = \
                inspect.getfullargspec(object)
            argspec = inspect.formatargspec(
                args, varargs, kwonlyargs, kwdefaults, varkw, defaults, ann,
                formatvalue=self.formatvalue,
                formatannotation=inspect.formatannotationrelativeto(object))
            if realname == '<lambda>':
                title = '<strong>%s</strong> <em>lambda</em> ' % name
                # XXX lambda's won't usually have func_annotations['return']
                # since the syntax doesn't support but it is possible.
                # So removing parentheses isn't truly safe.
                argspec = argspec[1:-1] # remove parentheses
        else:
            argspec = '(...)'

        decl = title + argspec + (note and self.grey(
               '<font face="helvetica, arial">%s</font>' % note))

        if skipdocs:
            return '<dl><dt>%s</dt></dl>\n' % decl
        else:
            doc = self.markup(
                getdoc(object), self.preformat, funcs, classes, methods)
            doc = doc and '<dd><tt>%s</tt></dd>' % doc
            return '<dl><dt>%s</dt>%s</dl>\n' % (decl, doc)

    def _docdescriptor(self, name, value, mod):
        results = []
        push = results.append

        if name:
            push('<dl><dt><strong>%s</strong></dt>\n' % name)
        if value.__doc__ is not None:
            doc = self.markup(getdoc(value), self.preformat)
            push('<dd><tt>%s</tt></dd>\n' % doc)
        push('</dl>\n')

        return ''.join(results)

    def docproperty(self, object, name=None, mod=None, cl=None):
        """Produce html documentation for a property."""
        return self._docdescriptor(name, object, mod)

    def docother(self, object, name=None, mod=None, *ignored):
        """Produce HTML documentation for a data object."""
        lhs = name and '<strong>%s</strong> = ' % name or ''
        return lhs + self.repr(object)

    def docdata(self, object, name=None, mod=None, cl=None):
        """Produce html documentation for a data descriptor."""
        return self._docdescriptor(name, object, mod)

    def index(self, dir, shadowed=None):
        """Generate an HTML index for a directory of modules."""
        modpkgs = []
        if shadowed is None: shadowed = {}
        for importer, name, ispkg in pkgutil.iter_modules([dir]):
            modpkgs.append((name, '', ispkg, name in shadowed))
            shadowed[name] = 1

        modpkgs.sort()
        contents = self.multicolumn(modpkgs, self.modpkglink)
        return self.bigsection(dir, '#ffffff', '#ee77aa', contents)

# -------------------------------------------- text documentation generator

class TextRepr(Repr):
    """Class for safely making a text representation of a Python object."""
    def __init__(self):
        Repr.__init__(self)
        self.maxlist = self.maxtuple = 20
        self.maxdict = 10
        self.maxstring = self.maxother = 100

    def repr1(self, x, level):
        if hasattr(type(x), '__name__'):
            methodname = 'repr_' + '_'.join(type(x).__name__.split())
            if hasattr(self, methodname):
                return getattr(self, methodname)(x, level)
        return cram(stripid(repr(x)), self.maxother)

    def repr_string(self, x, level):
        test = cram(x, self.maxstring)
        testrepr = repr(test)
        if '\\' in test and '\\' not in replace(testrepr, r'\\', ''):
            # Backslashes are only literal in the string and are never
            # needed to make any special characters, so show a raw string.
            return 'r' + testrepr[0] + test + testrepr[0]
        return testrepr

    repr_str = repr_string

    def repr_instance(self, x, level):
        try:
            return cram(stripid(repr(x)), self.maxstring)
        except:
            return '<%s instance>' % x.__class__.__name__

class TextDoc(Doc):
    """Formatter class for text documentation."""

    # ------------------------------------------- text formatting utilities

    _repr_instance = TextRepr()
    repr = _repr_instance.repr

    def bold(self, text):
        """Format a string in bold by overstriking."""
        return ''.join(map(lambda ch: ch + '\b' + ch, text))

    def indent(self, text, prefix='    '):
        """Indent text by prepending a given prefix to each line."""
        if not text: return ''
        lines = [prefix + line for line in text.split('\n')]
        if lines: lines[-1] = lines[-1].rstrip()
        return '\n'.join(lines)

    def section(self, title, contents):
        """Format a section with a given heading."""
        clean_contents = self.indent(contents).rstrip()
        return self.bold(title) + '\n' + clean_contents + '\n\n'

    # ---------------------------------------------- type-specific routines

    def formattree(self, tree, modname, parent=None, prefix=''):
        """Render in text a class tree as returned by inspect.getclasstree()."""
        result = ''
        for entry in tree:
            if type(entry) is type(()):
                c, bases = entry
                result = result + prefix + classname(c, modname)
                if bases and bases != (parent,):
                    parents = map(lambda c, m=modname: classname(c, m), bases)
                    result = result + '(%s)' % ', '.join(parents)
                result = result + '\n'
            elif type(entry) is type([]):
                result = result + self.formattree(
                    entry, modname, c, prefix + '    ')
        return result

    def docmodule(self, object, name=None, mod=None):
        """Produce text documentation for a given module object."""
        name = object.__name__ # ignore the passed-in name
        synop, desc = splitdoc(getdoc(object))
        result = self.section('NAME', name + (synop and ' - ' + synop))

        try:
            all = object.__all__
        except AttributeError:
            all = None

        try:
            file = inspect.getabsfile(object)
        except TypeError:
            file = '(built-in)'
        result = result + self.section('FILE', file)

        docloc = self.getdocloc(object)
        if docloc is not None:
            result = result + self.section('MODULE DOCS', docloc)

        if desc:
            result = result + self.section('DESCRIPTION', desc)

        classes = []
        for key, value in inspect.getmembers(object, inspect.isclass):
            # if __all__ exists, believe it.  Otherwise use old heuristic.
            if (all is not None
                or (inspect.getmodule(value) or object) is object):
                if visiblename(key, all):
                    classes.append((key, value))
        funcs = []
        for key, value in inspect.getmembers(object, inspect.isroutine):
            # if __all__ exists, believe it.  Otherwise use old heuristic.
            if (all is not None or
                inspect.isbuiltin(value) or inspect.getmodule(value) is object):
                if visiblename(key, all):
                    funcs.append((key, value))
        data = []
        for key, value in inspect.getmembers(object, isdata):
            if visiblename(key, all):
                data.append((key, value))

        modpkgs = []
        modpkgs_names = set()
        if hasattr(object, '__path__'):
            for importer, modname, ispkg in pkgutil.iter_modules(object.__path__):
                modpkgs_names.add(modname)
                if ispkg:
                    modpkgs.append(modname + ' (package)')
                else:
                    modpkgs.append(modname)

            modpkgs.sort()
            result = result + self.section(
                'PACKAGE CONTENTS', '\n'.join(modpkgs))

        # Detect submodules as sometimes created by C extensions
        submodules = []
        for key, value in inspect.getmembers(object, inspect.ismodule):
            if value.__name__.startswith(name + '.') and key not in modpkgs_names:
                submodules.append(key)
        if submodules:
            submodules.sort()
            result = result + self.section(
                'SUBMODULES', '\n'.join(submodules))

        if classes:
            classlist = [value for key, value in classes]
            contents = [self.formattree(
                inspect.getclasstree(classlist, 1), name)]
            for key, value in classes:
                contents.append(self.document(value, key, name))
            result = result + self.section('CLASSES', '\n'.join(contents))

        if funcs:
            contents = []
            for key, value in funcs:
                contents.append(self.document(value, key, name))
            result = result + self.section('FUNCTIONS', '\n'.join(contents))

        if data:
            contents = []
            for key, value in data:
                contents.append(self.docother(value, key, name, maxlen=70))
            result = result + self.section('DATA', '\n'.join(contents))

        if hasattr(object, '__version__'):
            version = str(object.__version__)
            if version[:11] == '$' + 'Revision: ' and version[-1:] == '$':
                version = version[11:-1].strip()
            result = result + self.section('VERSION', version)
        if hasattr(object, '__date__'):
            result = result + self.section('DATE', str(object.__date__))
        if hasattr(object, '__author__'):
            result = result + self.section('AUTHOR', str(object.__author__))
        if hasattr(object, '__credits__'):
            result = result + self.section('CREDITS', str(object.__credits__))
        return result

    def docclass(self, object, name=None, mod=None):
        """Produce text documentation for a given class object."""
        realname = object.__name__
        name = name or realname
        bases = object.__bases__

        def makename(c, m=object.__module__):
            return classname(c, m)

        if name == realname:
            title = 'class ' + self.bold(realname)
        else:
            title = self.bold(name) + ' = class ' + realname
        if bases:
            parents = map(makename, bases)
            title = title + '(%s)' % ', '.join(parents)

        doc = getdoc(object)
        contents = doc and [doc + '\n'] or []
        push = contents.append

        # List the mro, if non-trivial.
        mro = deque(inspect.getmro(object))
        if len(mro) > 2:
            push("Method resolution order:")
            for base in mro:
                push('    ' + makename(base))
            push('')

        # Cute little class to pump out a horizontal rule between sections.
        class HorizontalRule:
            def __init__(self):
                self.needone = 0
            def maybe(self):
                if self.needone:
                    push('-' * 70)
                self.needone = 1
        hr = HorizontalRule()

        def spill(msg, attrs, predicate):
            ok, attrs = _split_list(attrs, predicate)
            if ok:
                hr.maybe()
                push(msg)
                for name, kind, homecls, value in ok:
                    push(self.document(getattr(object, name),
                                       name, mod, object))
            return attrs

        def spilldescriptors(msg, attrs, predicate):
            ok, attrs = _split_list(attrs, predicate)
            if ok:
                hr.maybe()
                push(msg)
                for name, kind, homecls, value in ok:
                    push(self._docdescriptor(name, value, mod))
            return attrs

        def spilldata(msg, attrs, predicate):
            ok, attrs = _split_list(attrs, predicate)
            if ok:
                hr.maybe()
                push(msg)
                for name, kind, homecls, value in ok:
                    if hasattr(value, '__call__') or inspect.isdatadescriptor(value):
                        doc = getdoc(value)
                    else:
                        doc = None
                    push(self.docother(getattr(object, name),
                                       name, mod, maxlen=70, doc=doc) + '\n')
            return attrs

        attrs = [(name, kind, cls, value)
                 for name, kind, cls, value in classify_class_attrs(object)
                 if visiblename(name)]

        while attrs:
            if mro:
                thisclass = mro.popleft()
            else:
                thisclass = attrs[0][2]
            attrs, inherited = _split_list(attrs, lambda t: t[2] is thisclass)

            if thisclass is builtins.object:
                attrs = inherited
                continue
            elif thisclass is object:
                tag = "defined here"
            else:
                tag = "inherited from %s" % classname(thisclass,
                                                      object.__module__)

            # Sort attrs by name.
            attrs.sort()

            # Pump out the attrs, segregated by kind.
            attrs = spill("Methods %s:\n" % tag, attrs,
                          lambda t: t[1] == 'method')
            attrs = spill("Class methods %s:\n" % tag, attrs,
                          lambda t: t[1] == 'class method')
            attrs = spill("Static methods %s:\n" % tag, attrs,
                          lambda t: t[1] == 'static method')
            attrs = spilldescriptors("Data descriptors %s:\n" % tag, attrs,
                                     lambda t: t[1] == 'data descriptor')
            attrs = spilldata("Data and other attributes %s:\n" % tag, attrs,
                              lambda t: t[1] == 'data')
            assert attrs == []
            attrs = inherited

        contents = '\n'.join(contents)
        if not contents:
            return title + '\n'
        return title + '\n' + self.indent(contents.rstrip(), ' |  ') + '\n'

    def formatvalue(self, object):
        """Format an argument default value as text."""
        return '=' + self.repr(object)

    def docroutine(self, object, name=None, mod=None, cl=None):
        """Produce text documentation for a function or method object."""
        realname = object.__name__
        name = name or realname
        note = ''
        skipdocs = 0
        if inspect.ismethod(object):
            imclass = object.__self__.__class__
            if cl:
                if imclass is not cl:
                    note = ' from ' + classname(imclass, mod)
            else:
                if object.__self__ is not None:
                    note = ' method of %s instance' % classname(
                        object.__self__.__class__, mod)
                else:
                    note = ' unbound %s method' % classname(imclass,mod)
            object = object.__func__

        if name == realname:
            title = self.bold(realname)
        else:
            if (cl and realname in cl.__dict__ and
                cl.__dict__[realname] is object):
                skipdocs = 1
            title = self.bold(name) + ' = ' + realname
        if inspect.isfunction(object):
            args, varargs, varkw, defaults, kwonlyargs, kwdefaults, ann = \
              inspect.getfullargspec(object)
            argspec = inspect.formatargspec(
                args, varargs, varkw, defaults, kwonlyargs, kwdefaults, ann,
                formatvalue=self.formatvalue,
                formatannotation=inspect.formatannotationrelativeto(object))
            if realname == '<lambda>':
                title = self.bold(name) + ' lambda '
                # XXX lambda's won't usually have func_annotations['return']
                # since the syntax doesn't support but it is possible.
                # So removing parentheses isn't truly safe.
                argspec = argspec[1:-1] # remove parentheses
        else:
            argspec = '(...)'
        decl = title + argspec + note

        if skipdocs:
            return decl + '\n'
        else:
            doc = getdoc(object) or ''
            return decl + '\n' + (doc and self.indent(doc).rstrip() + '\n')

    def _docdescriptor(self, name, value, mod):
        results = []
        push = results.append

        if name:
            push(self.bold(name))
            push('\n')
        doc = getdoc(value) or ''
        if doc:
            push(self.indent(doc))
            push('\n')
        return ''.join(results)

    def docproperty(self, object, name=None, mod=None, cl=None):
        """Produce text documentation for a property."""
        return self._docdescriptor(name, object, mod)

    def docdata(self, object, name=None, mod=None, cl=None):
        """Produce text documentation for a data descriptor."""
        return self._docdescriptor(name, object, mod)

    def docother(self, object, name=None, mod=None, parent=None, maxlen=None, doc=None):
        """Produce text documentation for a data object."""
        repr = self.repr(object)
        if maxlen:
            line = (name and name + ' = ' or '') + repr
            chop = maxlen - len(line)
            if chop < 0: repr = repr[:chop] + '...'
        line = (name and self.bold(name) + ' = ' or '') + repr
        if doc is not None:
            line += '\n' + self.indent(str(doc))
        return line

# --------------------------------------------------------- user interfaces

def pager(text):
    """The first time this is called, determine what kind of pager to use."""
    global pager
    pager = getpager()
    pager(text)

def getpager():
    """Decide what method to use for paging through text."""
    if not hasattr(sys.stdout, "isatty"):
        return plainpager
    if not sys.stdin.isatty() or not sys.stdout.isatty():
        return plainpager
    if 'PAGER' in os.environ:
        if sys.platform == 'win32': # pipes completely broken in Windows
            return lambda text: tempfilepager(plain(text), os.environ['PAGER'])
        elif os.environ.get('TERM') in ('dumb', 'emacs'):
            return lambda text: pipepager(plain(text), os.environ['PAGER'])
        else:
            return lambda text: pipepager(text, os.environ['PAGER'])
    if os.environ.get('TERM') in ('dumb', 'emacs'):
        return plainpager
    if sys.platform == 'win32' or sys.platform.startswith('os2'):
        return lambda text: tempfilepager(plain(text), 'more <')
    if hasattr(os, 'system') and os.system('(less) 2>/dev/null') == 0:
        return lambda text: pipepager(text, 'less')

    import tempfile
    (fd, filename) = tempfile.mkstemp()
    os.close(fd)
    try:
        if hasattr(os, 'system') and os.system('more "%s"' % filename) == 0:
            return lambda text: pipepager(text, 'more')
        else:
            return ttypager
    finally:
        os.unlink(filename)

def plain(text):
    """Remove boldface formatting from text."""
    return re.sub('.\b', '', text)

def pipepager(text, cmd):
    """Page through text by feeding it to another program."""
    pipe = os.popen(cmd, 'w')
    try:
        pipe.write(text)
        pipe.close()
    except IOError:
        pass # Ignore broken pipes caused by quitting the pager program.

def tempfilepager(text, cmd):
    """Page through text by invoking a program on a temporary file."""
    import tempfile
    filename = tempfile.mktemp()
    file = open(filename, 'w')
    file.write(text)
    file.close()
    try:
        os.system(cmd + ' "' + filename + '"')
    finally:
        os.unlink(filename)

def ttypager(text):
    """Page through text on a text terminal."""
    lines = plain(text).split('\n')
    try:
        import tty
        fd = sys.stdin.fileno()
        old = tty.tcgetattr(fd)
        tty.setcbreak(fd)
        getchar = lambda: sys.stdin.read(1)
    except (ImportError, AttributeError):
        tty = None
        getchar = lambda: sys.stdin.readline()[:-1][:1]

    try:
        r = inc = os.environ.get('LINES', 25) - 1
        sys.stdout.write('\n'.join(lines[:inc]) + '\n')
        while lines[r:]:
            sys.stdout.write('-- more --')
            sys.stdout.flush()
            c = getchar()

            if c in ('q', 'Q'):
                sys.stdout.write('\r          \r')
                break
            elif c in ('\r', '\n'):
                sys.stdout.write('\r          \r' + lines[r] + '\n')
                r = r + 1
                continue
            if c in ('b', 'B', '\x1b'):
                r = r - inc - inc
                if r < 0: r = 0
            sys.stdout.write('\n' + '\n'.join(lines[r:r+inc]) + '\n')
            r = r + inc

    finally:
        if tty:
            tty.tcsetattr(fd, tty.TCSAFLUSH, old)

def plainpager(text):
    """Simply print unformatted text.  This is the ultimate fallback."""
    sys.stdout.write(plain(text))

def describe(thing):
    """Produce a short description of the given thing."""
    if inspect.ismodule(thing):
        if thing.__name__ in sys.builtin_module_names:
            return 'built-in module ' + thing.__name__
        if hasattr(thing, '__path__'):
            return 'package ' + thing.__name__
        else:
            return 'module ' + thing.__name__
    if inspect.isbuiltin(thing):
        return 'built-in function ' + thing.__name__
    if inspect.isgetsetdescriptor(thing):
        return 'getset descriptor %s.%s.%s' % (
            thing.__objclass__.__module__, thing.__objclass__.__name__,
            thing.__name__)
    if inspect.ismemberdescriptor(thing):
        return 'member descriptor %s.%s.%s' % (
            thing.__objclass__.__module__, thing.__objclass__.__name__,
            thing.__name__)
    if inspect.isclass(thing):
        return 'class ' + thing.__name__
    if inspect.isfunction(thing):
        return 'function ' + thing.__name__
    if inspect.ismethod(thing):
        return 'method ' + thing.__name__
    return type(thing).__name__

def locate(path, forceload=0):
    """Locate an object by name or dotted path, importing as necessary."""
    parts = [part for part in path.split('.') if part]
    module, n = None, 0
    while n < len(parts):
        nextmodule = safeimport('.'.join(parts[:n+1]), forceload)
        if nextmodule: module, n = nextmodule, n + 1
        else: break
    if module:
        object = module
        for part in parts[n:]:
            try: object = getattr(object, part)
            except AttributeError: return None
        return object
    else:
        if hasattr(builtins, path):
            return getattr(builtins, path)

# --------------------------------------- interactive interpreter interface

text = TextDoc()
html = HTMLDoc()

def resolve(thing, forceload=0):
    """Given an object or a path to an object, get the object and its name."""
    if isinstance(thing, str):
        object = locate(thing, forceload)
        if not object:
            raise ImportError('no Python documentation found for %r' % thing)
        return object, thing
    else:
        return thing, getattr(thing, '__name__', None)

def render_doc(thing, title='Python Library Documentation: %s', forceload=0):
    """Render text documentation, given an object or a path to an object."""
    object, name = resolve(thing, forceload)
    desc = describe(object)
    module = inspect.getmodule(object)
    if name and '.' in name:
        desc += ' in ' + name[:name.rfind('.')]
    elif module and module is not object:
        desc += ' in module ' + module.__name__

    if not (inspect.ismodule(object) or
              inspect.isclass(object) or
              inspect.isroutine(object) or
              inspect.isgetsetdescriptor(object) or
              inspect.ismemberdescriptor(object) or
              isinstance(object, property)):
        # If the passed object is a piece of data or an instance,
        # document its available methods instead of its value.
        object = type(object)
        desc += ' object'
    return title % desc + '\n\n' + text.document(object, name)

def doc(thing, title='Python Library Documentation: %s', forceload=0):
    """Display text documentation, given an object or a path to an object."""
    try:
        pager(render_doc(thing, title, forceload))
    except (ImportError, ErrorDuringImport) as value:
        print(value)

def writedoc(thing, forceload=0):
    """Write HTML documentation to a file in the current directory."""
    try:
        object, name = resolve(thing, forceload)
        page = html.page(describe(object), html.document(object, name))
        file = open(name + '.html', 'w')
        file.write(page)
        file.close()
        print('wrote', name + '.html')
    except (ImportError, ErrorDuringImport) as value:
        print(value)

def writedocs(dir, pkgpath='', done=None):
    """Write out HTML documentation for all modules in a directory tree."""
    if done is None: done = {}
    for importer, modname, ispkg in pkgutil.walk_packages([dir], pkgpath):
        writedoc(modname)
    return

class Helper:

    # These dictionaries map a topic name to either an alias, or a tuple
    # (label, seealso-items).  The "label" is the label of the corresponding
    # section in the .rst file under Doc/ and an index into the dictionary
    # in pydoc_topics.py.
    #
    # CAUTION: if you change one of these dictionaries, be sure to adapt the
    #          list of needed labels in Doc/tools/sphinxext/pyspecific.py and
    #          regenerate the pydoc_topics.py file by running
    #              make pydoc-topics
    #          in Doc/ and copying the output file into the Lib/ directory.

    keywords = {
        'and': 'BOOLEAN',
        'as': 'with',
        'assert': ('assert', ''),
        'break': ('break', 'while for'),
        'class': ('class', 'CLASSES SPECIALMETHODS'),
        'continue': ('continue', 'while for'),
        'def': ('function', ''),
        'del': ('del', 'BASICMETHODS'),
        'elif': 'if',
        'else': ('else', 'while for'),
        'except': 'try',
        'finally': 'try',
        'for': ('for', 'break continue while'),
        'from': 'import',
        'global': ('global', 'NAMESPACES'),
        'if': ('if', 'TRUTHVALUE'),
        'import': ('import', 'MODULES'),
        'in': ('in', 'SEQUENCEMETHODS2'),
        'is': 'COMPARISON',
        'lambda': ('lambda', 'FUNCTIONS'),
        'not': 'BOOLEAN',
        'or': 'BOOLEAN',
        'pass': ('pass', ''),
        'raise': ('raise', 'EXCEPTIONS'),
        'return': ('return', 'FUNCTIONS'),
        'try': ('try', 'EXCEPTIONS'),
        'while': ('while', 'break continue if TRUTHVALUE'),
        'with': ('with', 'CONTEXTMANAGERS EXCEPTIONS yield'),
        'yield': ('yield', ''),
    }
    # Either add symbols to this dictionary or to the symbols dictionary
    # directly: Whichever is easier. They are merged later.
    _symbols_inverse = {
        'STRINGS' : ("'", "'''", "r'", "b'", '"""', '"', 'r"', 'b"'),
        'OPERATORS' : ('+', '-', '*', '**', '/', '//', '%', '<<', '>>', '&',
                       '|', '^', '~', '<', '>', '<=', '>=', '==', '!=', '<>'),
        'COMPARISON' : ('<', '>', '<=', '>=', '==', '!=', '<>'),
        'UNARY' : ('-', '~'),
        'AUGMENTEDASSIGNMENT' : ('+=', '-=', '*=', '/=', '%=', '&=', '|=',
                                '^=', '<<=', '>>=', '**=', '//='),
        'BITWISE' : ('<<', '>>', '&', '|', '^', '~'),
        'COMPLEX' : ('j', 'J')
    }
    symbols = {
        '%': 'OPERATORS FORMATTING',
        '**': 'POWER',
        ',': 'TUPLES LISTS FUNCTIONS',
        '.': 'ATTRIBUTES FLOAT MODULES OBJECTS',
        '...': 'ELLIPSIS',
        ':': 'SLICINGS DICTIONARYLITERALS',
        '@': 'def class',
        '\\': 'STRINGS',
        '_': 'PRIVATENAMES',
        '__': 'PRIVATENAMES SPECIALMETHODS',
        '`': 'BACKQUOTES',
        '(': 'TUPLES FUNCTIONS CALLS',
        ')': 'TUPLES FUNCTIONS CALLS',
        '[': 'LISTS SUBSCRIPTS SLICINGS',
        ']': 'LISTS SUBSCRIPTS SLICINGS'
    }
    for topic, symbols_ in _symbols_inverse.items():
        for symbol in symbols_:
            topics = symbols.get(symbol, topic)
            if topic not in topics:
                topics = topics + ' ' + topic
            symbols[symbol] = topics

    topics = {
        'TYPES': ('types', 'STRINGS UNICODE NUMBERS SEQUENCES MAPPINGS '
                  'FUNCTIONS CLASSES MODULES FILES inspect'),
        'STRINGS': ('strings', 'str UNICODE SEQUENCES STRINGMETHODS '
                    'FORMATTING TYPES'),
        'STRINGMETHODS': ('string-methods', 'STRINGS FORMATTING'),
        'FORMATTING': ('formatstrings', 'OPERATORS'),
        'UNICODE': ('strings', 'encodings unicode SEQUENCES STRINGMETHODS '
                    'FORMATTING TYPES'),
        'NUMBERS': ('numbers', 'INTEGER FLOAT COMPLEX TYPES'),
        'INTEGER': ('integers', 'int range'),
        'FLOAT': ('floating', 'float math'),
        'COMPLEX': ('imaginary', 'complex cmath'),
        'SEQUENCES': ('typesseq', 'STRINGMETHODS FORMATTING range LISTS'),
        'MAPPINGS': 'DICTIONARIES',
        'FUNCTIONS': ('typesfunctions', 'def TYPES'),
        'METHODS': ('typesmethods', 'class def CLASSES TYPES'),
        'CODEOBJECTS': ('bltin-code-objects', 'compile FUNCTIONS TYPES'),
        'TYPEOBJECTS': ('bltin-type-objects', 'types TYPES'),
        'FRAMEOBJECTS': 'TYPES',
        'TRACEBACKS': 'TYPES',
        'NONE': ('bltin-null-object', ''),
        'ELLIPSIS': ('bltin-ellipsis-object', 'SLICINGS'),
        'FILES': ('bltin-file-objects', ''),
        'SPECIALATTRIBUTES': ('specialattrs', ''),
        'CLASSES': ('types', 'class SPECIALMETHODS PRIVATENAMES'),
        'MODULES': ('typesmodules', 'import'),
        'PACKAGES': 'import',
        'EXPRESSIONS': ('operator-summary', 'lambda or and not in is BOOLEAN '
                        'COMPARISON BITWISE SHIFTING BINARY FORMATTING POWER '
                        'UNARY ATTRIBUTES SUBSCRIPTS SLICINGS CALLS TUPLES '
                        'LISTS DICTIONARIES'),
        'OPERATORS': 'EXPRESSIONS',
        'PRECEDENCE': 'EXPRESSIONS',
        'OBJECTS': ('objects', 'TYPES'),
        'SPECIALMETHODS': ('specialnames', 'BASICMETHODS ATTRIBUTEMETHODS '
                           'CALLABLEMETHODS SEQUENCEMETHODS1 MAPPINGMETHODS '
                           'SEQUENCEMETHODS2 NUMBERMETHODS CLASSES'),
        'BASICMETHODS': ('customization', 'hash repr str SPECIALMETHODS'),
        'ATTRIBUTEMETHODS': ('attribute-access', 'ATTRIBUTES SPECIALMETHODS'),
        'CALLABLEMETHODS': ('callable-types', 'CALLS SPECIALMETHODS'),
        'SEQUENCEMETHODS': ('sequence-types', 'SEQUENCES SEQUENCEMETHODS2 '
                             'SPECIALMETHODS'),
        'MAPPINGMETHODS': ('sequence-types', 'MAPPINGS SPECIALMETHODS'),
        'NUMBERMETHODS': ('numeric-types', 'NUMBERS AUGMENTEDASSIGNMENT '
                          'SPECIALMETHODS'),
        'EXECUTION': ('execmodel', 'NAMESPACES DYNAMICFEATURES EXCEPTIONS'),
        'NAMESPACES': ('naming', 'global ASSIGNMENT DELETION DYNAMICFEATURES'),
        'DYNAMICFEATURES': ('dynamic-features', ''),
        'SCOPING': 'NAMESPACES',
        'FRAMES': 'NAMESPACES',
        'EXCEPTIONS': ('exceptions', 'try except finally raise'),
        'CONVERSIONS': ('conversions', ''),
        'IDENTIFIERS': ('identifiers', 'keywords SPECIALIDENTIFIERS'),
        'SPECIALIDENTIFIERS': ('id-classes', ''),
        'PRIVATENAMES': ('atom-identifiers', ''),
        'LITERALS': ('atom-literals', 'STRINGS NUMBERS TUPLELITERALS '
                     'LISTLITERALS DICTIONARYLITERALS'),
        'TUPLES': 'SEQUENCES',
        'TUPLELITERALS': ('exprlists', 'TUPLES LITERALS'),
        'LISTS': ('typesseq-mutable', 'LISTLITERALS'),
        'LISTLITERALS': ('lists', 'LISTS LITERALS'),
        'DICTIONARIES': ('typesmapping', 'DICTIONARYLITERALS'),
        'DICTIONARYLITERALS': ('dict', 'DICTIONARIES LITERALS'),
        'ATTRIBUTES': ('attribute-references', 'getattr hasattr setattr ATTRIBUTEMETHODS'),
        'SUBSCRIPTS': ('subscriptions', 'SEQUENCEMETHODS1'),
        'SLICINGS': ('slicings', 'SEQUENCEMETHODS2'),
        'CALLS': ('calls', 'EXPRESSIONS'),
        'POWER': ('power', 'EXPRESSIONS'),
        'UNARY': ('unary', 'EXPRESSIONS'),
        'BINARY': ('binary', 'EXPRESSIONS'),
        'SHIFTING': ('shifting', 'EXPRESSIONS'),
        'BITWISE': ('bitwise', 'EXPRESSIONS'),
        'COMPARISON': ('comparisons', 'EXPRESSIONS BASICMETHODS'),
        'BOOLEAN': ('booleans', 'EXPRESSIONS TRUTHVALUE'),
        'ASSERTION': 'assert',
        'ASSIGNMENT': ('assignment', 'AUGMENTEDASSIGNMENT'),
        'AUGMENTEDASSIGNMENT': ('augassign', 'NUMBERMETHODS'),
        'DELETION': 'del',
        'RETURNING': 'return',
        'IMPORTING': 'import',
        'CONDITIONAL': 'if',
        'LOOPING': ('compound', 'for while break continue'),
        'TRUTHVALUE': ('truth', 'if while and or not BASICMETHODS'),
        'DEBUGGING': ('debugger', 'pdb'),
        'CONTEXTMANAGERS': ('context-managers', 'with'),
    }

    def __init__(self, input, output):
        self.input = input
        self.output = output

    def __repr__(self):
        if inspect.stack()[1][3] == '?':
            self()
            return ''
        return '<pydoc.Helper instance>'

    def __call__(self, request=None):
        if request is not None:
            self.help(request)
        else:
            self.intro()
            self.interact()
            self.output.write('''
You are now leaving help and returning to the Python interpreter.
If you want to ask for help on a particular object directly from the
interpreter, you can type "help(object)".  Executing "help('string')"
has the same effect as typing a particular string at the help> prompt.
''')

    def interact(self):
        self.output.write('\n')
        while True:
            try:
                request = self.getline('help> ')
                if not request: break
            except (KeyboardInterrupt, EOFError):
                break
            request = replace(request, '"', '', "'", '').strip()
            if request.lower() in ('q', 'quit'): break
            self.help(request)

    def getline(self, prompt):
        """Read one line, using input() when appropriate."""
        if self.input is sys.stdin:
            return input(prompt)
        else:
            self.output.write(prompt)
            self.output.flush()
            return self.input.readline()

    def help(self, request):
        if type(request) is type(''):
            if request == 'help': self.intro()
            elif request == 'keywords': self.listkeywords()
            elif request == 'symbols': self.listsymbols()
            elif request == 'topics': self.listtopics()
            elif request == 'modules': self.listmodules()
            elif request[:8] == 'modules ':
                self.listmodules(request.split()[1])
            elif request in self.symbols: self.showsymbol(request)
            elif request in self.keywords: self.showtopic(request)
            elif request in self.topics: self.showtopic(request)
            elif request: doc(request, 'Help on %s:')
        elif isinstance(request, Helper): self()
        else: doc(request, 'Help on %s:')
        self.output.write('\n')

    def intro(self):
        self.output.write('''
Welcome to Python %s!  This is the online help utility.

If this is your first time using Python, you should definitely check out
the tutorial on the Internet at http://docs.python.org/tutorial/.

Enter the name of any module, keyword, or topic to get help on writing
Python programs and using Python modules.  To quit this help utility and
return to the interpreter, just type "quit".

To get a list of available modules, keywords, or topics, type "modules",
"keywords", or "topics".  Each module also comes with a one-line summary
of what it does; to list the modules whose summaries contain a given word
such as "spam", type "modules spam".
''' % sys.version[:3])

    def list(self, items, columns=4, width=80):
        items = list(sorted(items))
        colw = width // columns
        rows = (len(items) + columns - 1) // columns
        for row in range(rows):
            for col in range(columns):
                i = col * rows + row
                if i < len(items):
                    self.output.write(items[i])
                    if col < columns - 1:
                        self.output.write(' ' + ' ' * (colw - 1 - len(items[i])))
            self.output.write('\n')

    def listkeywords(self):
        self.output.write('''
Here is a list of the Python keywords.  Enter any keyword to get more help.

''')
        self.list(self.keywords.keys())

    def listsymbols(self):
        self.output.write('''
Here is a list of the punctuation symbols which Python assigns special meaning
to. Enter any symbol to get more help.

''')
        self.list(self.symbols.keys())

    def listtopics(self):
        self.output.write('''
Here is a list of available topics.  Enter any topic name to get more help.

''')
        self.list(self.topics.keys())

    def showtopic(self, topic, more_xrefs=''):
        try:
            import pydoc_topics
        except ImportError:
            self.output.write('''
Sorry, topic and keyword documentation is not available because the
module "pydoc_topics" could not be found.
''')
            return
        target = self.topics.get(topic, self.keywords.get(topic))
        if not target:
            self.output.write('no documentation found for %s\n' % repr(topic))
            return
        if type(target) is type(''):
            return self.showtopic(target, more_xrefs)

        label, xrefs = target
        try:
            doc = pydoc_topics.topics[label]
        except KeyError:
            self.output.write('no documentation found for %s\n' % repr(topic))
            return
        pager(doc.strip() + '\n')
        if more_xrefs:
            xrefs = (xrefs or '') + ' ' + more_xrefs
        if xrefs:
            import io, formatter
            buffer = io.StringIO()
            formatter.DumbWriter(buffer).send_flowing_data(
                'Related help topics: ' + ', '.join(xrefs.split()) + '\n')
            self.output.write('\n%s\n' % buffer.getvalue())

    def showsymbol(self, symbol):
        target = self.symbols[symbol]
        topic, _, xrefs = target.partition(' ')
        self.showtopic(topic, xrefs)

    def listmodules(self, key=''):
        if key:
            self.output.write('''
Here is a list of matching modules.  Enter any module name to get more help.

''')
            apropos(key)
        else:
            self.output.write('''
Please wait a moment while I gather a list of all available modules...

''')
            modules = {}
            def callback(path, modname, desc, modules=modules):
                if modname and modname[-9:] == '.__init__':
                    modname = modname[:-9] + ' (package)'
                if modname.find('.') < 0:
                    modules[modname] = 1
            def onerror(modname):
                callback(None, modname, None)
            ModuleScanner().run(callback, onerror=onerror)
            self.list(modules.keys())
            self.output.write('''
Enter any module name to get more help.  Or, type "modules spam" to search
for modules whose descriptions contain the word "spam".
''')

help = Helper(sys.stdin, sys.stdout)

class Scanner:
    """A generic tree iterator."""
    def __init__(self, roots, children, descendp):
        self.roots = roots[:]
        self.state = []
        self.children = children
        self.descendp = descendp

    def next(self):
        if not self.state:
            if not self.roots:
                return None
            root = self.roots.pop(0)
            self.state = [(root, self.children(root))]
        node, children = self.state[-1]
        if not children:
            self.state.pop()
            return self.next()
        child = children.pop(0)
        if self.descendp(child):
            self.state.append((child, self.children(child)))
        return child


class ModuleScanner:
    """An interruptible scanner that searches module synopses."""

    def run(self, callback, key=None, completer=None, onerror=None):
        if key: key = key.lower()
        self.quit = False
        seen = {}

        for modname in sys.builtin_module_names:
            if modname != '__main__':
                seen[modname] = 1
                if key is None:
                    callback(None, modname, '')
                else:
                    name = __import__(modname).__doc__ or ''
                    desc = name.split('\n')[0]
                    name = modname + ' - ' + desc
                    if name.lower().find(key) >= 0:
                        callback(None, modname, desc)

        for importer, modname, ispkg in pkgutil.walk_packages(onerror=onerror):
            if self.quit:
                break
            if key is None:
                callback(None, modname, '')
            else:
                loader = importer.find_module(modname)
                if hasattr(loader,'get_source'):
                    try:
                        source = loader.get_source(modname)
                    except UnicodeDecodeError:
                        if onerror:
                            onerror(modname)
                        continue
                    import io
                    desc = source_synopsis(io.StringIO(source)) or ''
                    if hasattr(loader,'get_filename'):
                        path = loader.get_filename(modname)
                    else:
                        path = None
                else:
                    try:
                        module = loader.load_module(modname)
                    except ImportError:
                        if onerror:
                            onerror(modname)
                        continue
                    desc = (module.__doc__ or '').splitlines()[0]
                    path = getattr(module,'__file__',None)
                name = modname + ' - ' + desc
                if name.lower().find(key) >= 0:
                    callback(path, modname, desc)

        if completer:
            completer()

def apropos(key):
    """Print all the one-line module summaries that contain a substring."""
    def callback(path, modname, desc):
        if modname[-9:] == '.__init__':
            modname = modname[:-9] + ' (package)'
        print(modname, desc and '- ' + desc)
    def onerror(modname):
        pass
    try: import warnings
    except ImportError: pass
    else: warnings.filterwarnings('ignore') # ignore problems during import
    ModuleScanner().run(callback, key, onerror=onerror)

# --------------------------------------------------- web browser interface

def serve(port, callback=None, completer=None):
    import http.server, email.message, select

    class DocHandler(http.server.BaseHTTPRequestHandler):
        def send_document(self, title, contents):
            try:
                self.send_response(200)
                self.send_header('Content-Type', 'text/html; charset=UTF-8')
                self.end_headers()
                self.wfile.write(html.page(title, contents).encode('utf-8'))
            except IOError: pass

        def do_GET(self):
            path = self.path
            if path[-5:] == '.html': path = path[:-5]
            if path[:1] == '/': path = path[1:]
            if path and path != '.':
                try:
                    obj = locate(path, forceload=1)
                except ErrorDuringImport as value:
                    self.send_document(path, html.escape(str(value)))
                    return
                if obj:
                    self.send_document(describe(obj), html.document(obj, path))
                else:
                    self.send_document(path,
'no Python documentation found for %s' % repr(path))
            else:
                heading = html.heading(
'<big><big><strong>Python: Index of Modules</strong></big></big>',
'#ffffff', '#7799ee')
                def bltinlink(name):
                    return '<a href="%s.html">%s</a>' % (name, name)
                names = [x for x in sys.builtin_module_names if x != '__main__']
                contents = html.multicolumn(names, bltinlink)
                indices = ['<p>' + html.bigsection(
                    'Built-in Modules', '#ffffff', '#ee77aa', contents)]

                seen = {}
                for dir in sys.path:
                    indices.append(html.index(dir, seen))
                contents = heading + ' '.join(indices) + '''<p align=right>
<font color="#909090" face="helvetica, arial"><strong>
pydoc</strong> by Ka-Ping Yee &lt;ping@lfw.org&gt;</font>'''
                self.send_document('Index of Modules', contents)

        def log_message(self, *args): pass

    class DocServer(http.server.HTTPServer):
        def __init__(self, port, callback):
            host = (sys.platform == 'mac') and '127.0.0.1' or 'localhost'
            self.address = ('', port)
            self.url = 'http://%s:%d/' % (host, port)
            self.callback = callback
            self.base.__init__(self, self.address, self.handler)

        def serve_until_quit(self):
            import select
            self.quit = False
            while not self.quit:
                rd, wr, ex = select.select([self.socket.fileno()], [], [], 1)
                if rd: self.handle_request()

        def server_activate(self):
            self.base.server_activate(self)
            if self.callback: self.callback(self)

    DocServer.base = http.server.HTTPServer
    DocServer.handler = DocHandler
    DocHandler.MessageClass = email.message.Message
    try:
        try:
            DocServer(port, callback).serve_until_quit()
        except (KeyboardInterrupt, select.error):
            pass
    finally:
        if completer: completer()

# ----------------------------------------------------- graphical interface

def gui():
    """Graphical interface (starts web server and pops up a control window)."""
    class GUI:
        def __init__(self, window, port=7464):
            self.window = window
            self.server = None
            self.scanner = None

            import tkinter
            self.server_frm = tkinter.Frame(window)
            self.title_lbl = tkinter.Label(self.server_frm,
                text='Starting server...\n ')
            self.open_btn = tkinter.Button(self.server_frm,
                text='open browser', command=self.open, state='disabled')
            self.quit_btn = tkinter.Button(self.server_frm,
                text='quit serving', command=self.quit, state='disabled')

            self.search_frm = tkinter.Frame(window)
            self.search_lbl = tkinter.Label(self.search_frm, text='Search for')
            self.search_ent = tkinter.Entry(self.search_frm)
            self.search_ent.bind('<Return>', self.search)
            self.stop_btn = tkinter.Button(self.search_frm,
                text='stop', pady=0, command=self.stop, state='disabled')
            if sys.platform == 'win32':
                # Trying to hide and show this button crashes under Windows.
                self.stop_btn.pack(side='right')

            self.window.title('pydoc')
            self.window.protocol('WM_DELETE_WINDOW', self.quit)
            self.title_lbl.pack(side='top', fill='x')
            self.open_btn.pack(side='left', fill='x', expand=1)
            self.quit_btn.pack(side='right', fill='x', expand=1)
            self.server_frm.pack(side='top', fill='x')

            self.search_lbl.pack(side='left')
            self.search_ent.pack(side='right', fill='x', expand=1)
            self.search_frm.pack(side='top', fill='x')
            self.search_ent.focus_set()

            font = ('helvetica', sys.platform == 'win32' and 8 or 10)
            self.result_lst = tkinter.Listbox(window, font=font, height=6)
            self.result_lst.bind('<Button-1>', self.select)
            self.result_lst.bind('<Double-Button-1>', self.goto)
            self.result_scr = tkinter.Scrollbar(window,
                orient='vertical', command=self.result_lst.yview)
            self.result_lst.config(yscrollcommand=self.result_scr.set)

            self.result_frm = tkinter.Frame(window)
            self.goto_btn = tkinter.Button(self.result_frm,
                text='go to selected', command=self.goto)
            self.hide_btn = tkinter.Button(self.result_frm,
                text='hide results', command=self.hide)
            self.goto_btn.pack(side='left', fill='x', expand=1)
            self.hide_btn.pack(side='right', fill='x', expand=1)

            self.window.update()
            self.minwidth = self.window.winfo_width()
            self.minheight = self.window.winfo_height()
            self.bigminheight = (self.server_frm.winfo_reqheight() +
                                 self.search_frm.winfo_reqheight() +
                                 self.result_lst.winfo_reqheight() +
                                 self.result_frm.winfo_reqheight())
            self.bigwidth, self.bigheight = self.minwidth, self.bigminheight
            self.expanded = 0
            self.window.wm_geometry('%dx%d' % (self.minwidth, self.minheight))
            self.window.wm_minsize(self.minwidth, self.minheight)
            self.window.tk.willdispatch()

            import threading
            threading.Thread(
                target=serve, args=(port, self.ready, self.quit)).start()

        def ready(self, server):
            self.server = server
            self.title_lbl.config(
                text='Python documentation server at\n' + server.url)
            self.open_btn.config(state='normal')
            self.quit_btn.config(state='normal')

        def open(self, event=None, url=None):
            url = url or self.server.url
            try:
                import webbrowser
                webbrowser.open(url)
            except ImportError: # pre-webbrowser.py compatibility
                if sys.platform == 'win32':
                    os.system('start "%s"' % url)
                elif sys.platform == 'mac':
                    try: import ic
                    except ImportError: pass
                    else: ic.launchurl(url)
                else:
                    rc = os.system('netscape -remote "openURL(%s)" &' % url)
                    if rc: os.system('netscape "%s" &' % url)

        def quit(self, event=None):
            if self.server:
                self.server.quit = 1
            self.window.quit()

        def search(self, event=None):
            key = self.search_ent.get()
            self.stop_btn.pack(side='right')
            self.stop_btn.config(state='normal')
            self.search_lbl.config(text='Searching for "%s"...' % key)
            self.search_ent.forget()
            self.search_lbl.pack(side='left')
            self.result_lst.delete(0, 'end')
            self.goto_btn.config(state='disabled')
            self.expand()

            import threading
            if self.scanner:
                self.scanner.quit = 1
            self.scanner = ModuleScanner()
            threading.Thread(target=self.scanner.run,
                             args=(self.update, key, self.done)).start()

        def update(self, path, modname, desc):
            if modname[-9:] == '.__init__':
                modname = modname[:-9] + ' (package)'
            self.result_lst.insert('end',
                modname + ' - ' + (desc or '(no description)'))

        def stop(self, event=None):
            if self.scanner:
                self.scanner.quit = 1
                self.scanner = None

        def done(self):
            self.scanner = None
            self.search_lbl.config(text='Search for')
            self.search_lbl.pack(side='left')
            self.search_ent.pack(side='right', fill='x', expand=1)
            if sys.platform != 'win32': self.stop_btn.forget()
            self.stop_btn.config(state='disabled')

        def select(self, event=None):
            self.goto_btn.config(state='normal')

        def goto(self, event=None):
            selection = self.result_lst.curselection()
            if selection:
                modname = self.result_lst.get(selection[0]).split()[0]
                self.open(url=self.server.url + modname + '.html')

        def collapse(self):
            if not self.expanded: return
            self.result_frm.forget()
            self.result_scr.forget()
            self.result_lst.forget()
            self.bigwidth = self.window.winfo_width()
            self.bigheight = self.window.winfo_height()
            self.window.wm_geometry('%dx%d' % (self.minwidth, self.minheight))
            self.window.wm_minsize(self.minwidth, self.minheight)
            self.expanded = 0

        def expand(self):
            if self.expanded: return
            self.result_frm.pack(side='bottom', fill='x')
            self.result_scr.pack(side='right', fill='y')
            self.result_lst.pack(side='top', fill='both', expand=1)
            self.window.wm_geometry('%dx%d' % (self.bigwidth, self.bigheight))
            self.window.wm_minsize(self.minwidth, self.bigminheight)
            self.expanded = 1

        def hide(self, event=None):
            self.stop()
            self.collapse()

    import tkinter
    try:
        root = tkinter.Tk()
        # Tk will crash if pythonw.exe has an XP .manifest
        # file and the root has is not destroyed explicitly.
        # If the problem is ever fixed in Tk, the explicit
        # destroy can go.
        try:
            gui = GUI(root)
            root.mainloop()
        finally:
            root.destroy()
    except KeyboardInterrupt:
        pass

# -------------------------------------------------- command-line interface

def ispath(x):
    return isinstance(x, str) and x.find(os.sep) >= 0

def cli():
    """Command-line interface (looks at sys.argv to decide what to do)."""
    import getopt
    class BadUsage(Exception): pass

    # Scripts don't get the current directory in their path by default.
    scriptdir = os.path.dirname(sys.argv[0])
    if scriptdir in sys.path:
        sys.path.remove(scriptdir)
    sys.path.insert(0, '.')

    try:
        opts, args = getopt.getopt(sys.argv[1:], 'gk:p:w')
        writing = 0

        for opt, val in opts:
            if opt == '-g':
                gui()
                return
            if opt == '-k':
                apropos(val)
                return
            if opt == '-p':
                try:
                    port = int(val)
                except ValueError:
                    raise BadUsage
                def ready(server):
                    print('pydoc server ready at %s' % server.url)
                def stopped():
                    print('pydoc server stopped')
                serve(port, ready, stopped)
                return
            if opt == '-w':
                writing = 1

        if not args: raise BadUsage
        for arg in args:
            if ispath(arg) and not os.path.exists(arg):
                print('file %r does not exist' % arg)
                break
            try:
                if ispath(arg) and os.path.isfile(arg):
                    arg = importfile(arg)
                if writing:
                    if ispath(arg) and os.path.isdir(arg):
                        writedocs(arg)
                    else:
                        writedoc(arg)
                else:
                    help.help(arg)
            except ErrorDuringImport as value:
                print(value)

    except (getopt.error, BadUsage):
        cmd = os.path.basename(sys.argv[0])
        print("""pydoc - the Python documentation tool

%s <name> ...
    Show text documentation on something.  <name> may be the name of a
    Python keyword, topic, function, module, or package, or a dotted
    reference to a class or function within a module or module in a
    package.  If <name> contains a '%s', it is used as the path to a
    Python source file to document. If name is 'keywords', 'topics',
    or 'modules', a listing of these things is displayed.

%s -k <keyword>
    Search for a keyword in the synopsis lines of all available modules.

%s -p <port>
    Start an HTTP server on the given port on the local machine.

%s -g
    Pop up a graphical interface for finding and serving documentation.

%s -w <name> ...
    Write out the HTML documentation for a module to a file in the current
    directory.  If <name> contains a '%s', it is treated as a filename; if
    it names a directory, documentation is written for all the contents.
""" % (cmd, os.sep, cmd, cmd, cmd, cmd, os.sep))

if __name__ == '__main__': cli()