| # Author: Fred L. Drake, Jr. |
| # fdrake@cnri.reston.va.us, fdrake@acm.org |
| # |
| # This is a simple little module I wrote to make life easier. I didn't |
| # see anything quite like it in the library, though I may have overlooked |
| # something. I wrote this when I was trying to read some heavily nested |
| # tuples with fairly non-descriptive content. This is modeled very much |
| # after Lisp/Scheme - style pretty-printing of lists. If you find it |
| # useful, thank small children who sleep at night. |
| |
| """Support to pretty-print lists, tuples, & dictionaries recursively. |
| |
| Very simple, but useful, especially in debugging data structures. |
| |
| Classes |
| ------- |
| |
| PrettyPrinter() |
| Handle pretty-printing operations onto a stream using a configured |
| set of formatting parameters. |
| |
| Functions |
| --------- |
| |
| pformat() |
| Format a Python object into a pretty-printed representation. |
| |
| pprint() |
| Pretty-print a Python object to a stream [default is sys.sydout]. |
| |
| saferepr() |
| Generate a 'standard' repr()-like value, but protect against recursive |
| data structures. |
| |
| """ |
| |
| from types import DictType, ListType, TupleType |
| |
| try: |
| from cStringIO import StringIO |
| except ImportError: |
| from StringIO import StringIO |
| |
| __all__ = ["pprint","pformat","isreadable","isrecursive","saferepr", |
| "PrettyPrinter"] |
| |
| def pprint(object, stream=None): |
| """Pretty-print a Python object to a stream [default is sys.sydout].""" |
| printer = PrettyPrinter(stream=stream) |
| printer.pprint(object) |
| |
| |
| def pformat(object): |
| """Format a Python object into a pretty-printed representation.""" |
| return PrettyPrinter().pformat(object) |
| |
| |
| def isreadable(object): |
| """Determine if saferepr(object) is readable by eval().""" |
| return PrettyPrinter().isreadable(object) |
| |
| |
| def isrecursive(object): |
| """Determine if object requires a recursive representation.""" |
| return PrettyPrinter().isrecursive(object) |
| |
| |
| def saferepr(object): |
| """Version of repr() which can handle recursive data structures.""" |
| return _safe_repr(object, {})[0] |
| |
| |
| class PrettyPrinter: |
| def __init__(self, indent=1, width=80, depth=None, stream=None): |
| """Handle pretty printing operations onto a stream using a set of |
| configured parameters. |
| |
| indent |
| Number of spaces to indent for each level of nesting. |
| |
| width |
| Attempted maximum number of columns in the output. |
| |
| depth |
| The maximum depth to print out nested structures. |
| |
| stream |
| The desired output stream. If omitted (or false), the standard |
| output stream available at construction will be used. |
| |
| """ |
| indent = int(indent) |
| width = int(width) |
| assert indent >= 0 |
| assert (not depth) or depth > 0, "depth may not be negative" |
| assert width |
| self.__depth = depth |
| self.__indent_per_level = indent |
| self.__width = width |
| if stream: |
| self.__stream = stream |
| else: |
| import sys |
| self.__stream = sys.stdout |
| |
| def pprint(self, object): |
| self.__stream.write(self.pformat(object) + "\n") |
| |
| def pformat(self, object): |
| sio = StringIO() |
| self.__format(object, sio, 0, 0, {}, 0) |
| return sio.getvalue() |
| |
| def isrecursive(self, object): |
| self.__recursive = 0 |
| self.pformat(object) |
| return self.__recursive |
| |
| def isreadable(self, object): |
| self.__recursive = 0 |
| self.__readable = 1 |
| self.pformat(object) |
| return self.__readable and not self.__recursive |
| |
| def __format(self, object, stream, indent, allowance, context, level): |
| level = level + 1 |
| if context.has_key(id(object)): |
| object = _Recursion(object) |
| self.__recursive = 1 |
| rep = self.__repr(object, context, level - 1) |
| objid = id(object) |
| context[objid] = 1 |
| typ = type(object) |
| sepLines = len(rep) > (self.__width - 1 - indent - allowance) |
| |
| if sepLines and typ in (ListType, TupleType): |
| # Pretty-print the sequence. |
| stream.write((typ is ListType) and '[' or '(') |
| if self.__indent_per_level > 1: |
| stream.write((self.__indent_per_level - 1) * ' ') |
| length = len(object) |
| if length: |
| indent = indent + self.__indent_per_level |
| self.__format(object[0], stream, indent, allowance + 1, |
| context, level) |
| if length > 1: |
| for ent in object[1:]: |
| stream.write(',\n' + ' '*indent) |
| self.__format(ent, stream, indent, |
| allowance + 1, context, level) |
| indent = indent - self.__indent_per_level |
| if typ is TupleType and length == 1: |
| stream.write(',') |
| stream.write(((typ is ListType) and ']') or ')') |
| |
| elif sepLines and typ is DictType: |
| stream.write('{') |
| if self.__indent_per_level > 1: |
| stream.write((self.__indent_per_level - 1) * ' ') |
| length = len(object) |
| if length: |
| indent = indent + self.__indent_per_level |
| items = object.items() |
| items.sort() |
| key, ent = items[0] |
| rep = self.__repr(key, context, level) + ': ' |
| stream.write(rep) |
| self.__format(ent, stream, indent + len(rep), |
| allowance + 1, context, level) |
| if len(items) > 1: |
| for key, ent in items[1:]: |
| rep = self.__repr(key, context, level) + ': ' |
| stream.write(',\n' + ' '*indent + rep) |
| self.__format(ent, stream, indent + len(rep), |
| allowance + 1, context, level) |
| indent = indent - self.__indent_per_level |
| stream.write('}') |
| |
| else: |
| stream.write(rep) |
| |
| del context[objid] |
| |
| def __repr(self, object, context, level): |
| repr, readable = _safe_repr(object, context, self.__depth, level) |
| if not readable: |
| self.__readable = 0 |
| return repr |
| |
| |
| def _safe_repr(object, context, maxlevels=None, level=0): |
| level = level + 1 |
| typ = type(object) |
| if not (typ in (DictType, ListType, TupleType) and object): |
| rep = `object` |
| return rep, (rep and (rep[0] != '<')) |
| if context.has_key(id(object)): |
| return `_Recursion(object)`, 0 |
| objid = id(object) |
| context[objid] = 1 |
| readable = 1 |
| if typ is DictType: |
| if maxlevels and level >= maxlevels: |
| s = "{...}" |
| readable = 0 |
| else: |
| items = object.items() |
| k, v = items[0] |
| krepr, kreadable = _safe_repr(k, context, maxlevels, level) |
| vrepr, vreadable = _safe_repr(v, context, maxlevels, level) |
| readable = readable and kreadable and vreadable |
| s = "{%s: %s" % (krepr, vrepr) |
| for k, v in items[1:]: |
| krepr, kreadable = _safe_repr(k, context, maxlevels, level) |
| vrepr, vreadable = _safe_repr(v, context, maxlevels, level) |
| readable = readable and kreadable and vreadable |
| s = "%s, %s: %s" % (s, krepr, vrepr) |
| s = s + "}" |
| else: |
| s, term = (typ is ListType) and ('[', ']') or ('(', ')') |
| if maxlevels and level >= maxlevels: |
| s = s + "..." |
| readable = 0 |
| else: |
| subrepr, subreadable = _safe_repr( |
| object[0], context, maxlevels, level) |
| readable = readable and subreadable |
| s = s + subrepr |
| tail = object[1:] |
| if not tail: |
| if typ is TupleType: |
| s = s + ',' |
| for ent in tail: |
| subrepr, subreadable = _safe_repr( |
| ent, context, maxlevels, level) |
| readable = readable and subreadable |
| s = "%s, %s" % (s, subrepr) |
| s = s + term |
| del context[objid] |
| return s, readable |
| |
| |
| class _Recursion: |
| # represent a recursive relationship; really only used for the __repr__() |
| # method... |
| def __init__(self, object): |
| self.__repr = "<Recursion on %s with id=%s>" \ |
| % (type(object).__name__, id(object)) |
| |
| def __repr__(self): |
| return self.__repr |