Checking in patch 404826 -- urllib2 enhancements and documentations.
(please not that the library reference does *not* include the
urllib2 documnetation -- that will wiat for Fred)
diff --git a/Doc/lib/liburllib2.tex b/Doc/lib/liburllib2.tex
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+\section{\module{urllib2} ---
+ extensible library for opening URLs}
+
+\declaremodule{standard}{urllib2}
+
+\moduleauthor{Jeremy Hylton}{jhylton@users.sourceforge.net}
+\sectionauthor{Moshe Zadka}{moshez@users.sourceforge.net}
+
+\modulesynopsis{An extensible library for opening URLs using a variety of
+ protocols}
+
+The \module{urllib2} module defines functions and classes which help
+in opening URLs (mostly HTTP) in a complex world -- basic and digest
+authentication, redirections and more.
+
+The \module{urllib2} module defines the following functions:
+
+\begin{funcdesc}{urlopen}{url\optional{, data}}
+Open the url \var{url}, which can either a string or a \class{Request}
+object (currently the code checks that it really is a \class{Request}
+instance, or an instance of a subclass of \class{Request}.
+
+\var{data} should be a string, which specifies additional data to
+send to the server. In HTTP requests, which are the only ones that
+support \var{data}, it should be a buffer in the format of
+\code{application/x-www-form-urlencoded}, for example one returned
+from \function{urllib.urlencode}.
+
+This function returns a file-like object with two additional methods:
+
+\begin{itemize}
+
+ \item \code{geturl()} --- return the URL of the resource retrieved
+ \item \code{info()} --- return the meta-information of the page, as
+ a dictionary-like object
+\end{itemize}
+
+Raises \exception{URLError} on errors.
+\end{funcdesc}
+
+\begin{funcdesc}{install_opener}{opener}
+Install a \class{OpenerDirector} instance as the default opener.
+The code does not check for a real \class{OpenerDirector}, and any
+class with the appropriate interface will work.
+\end{funcdesc}
+
+\begin{funcdesc}{build_opener}{\optional{handler\optional{,
+ handler\optional{, ...}}}}
+Return an \class{OpenerDirector} instance, which chains the
+handlers in the order given. \var{handler}s can be either instances
+of \class{BaseHandler}, or subclasses of \class{BaseHandler} (in
+which case it must be possible to call the constructor without
+any parameters. Instances of the following classes will be in
+the front of the \var{handler}s, unless the \var{handler}s contain
+them, instances of them or subclasses of them:
+
+\code{ProxyHandler, UnknownHandler, HTTPHandler, HTTPDefaultErrorHandler,
+ HTTPRedirectHandler, FTPHandler, FileHandler}
+
+If the Python installation has SSL support (\code{socket.ssl} exists),
+\class{HTTPSHandler} will also be added.
+\end{funcdesc}
+
+\begin{excdesc}{URLError}
+The error handlers raise when they run into a problem. It is a subclass
+of \exception{IOError}.
+\end{excdesc}
+
+\begin{excdesc}{HTTPError}
+A subclass of \exception{URLError}, it can also function as a
+non-exceptional file-like return value (the same thing that \function{urlopen}
+returns). This is useful when handling exotic HTTP errors, such as
+requests for authentications.
+\end{excdesc}
+
+\begin{excdesc}{GopherError}
+A subclass of \exception{URLError}, this is the error raised by the
+Gopher handler.
+\end{excdesc}
+
+\begin{classdesc}{Request}{url\optional{data, \optional{, headers}}}
+This class is an abstraction of a URL request.
+
+\var{url} should be a string which is a valid URL. For descrtion
+of \var{data} see the \method{add_data} description.
+\var{headers} should be a dictionary, and will be treated as if
+\method{add_header} was called with each key and value as arguments.
+\end{classdesc}
+
+The following methods describe all of \class{Request}'s public interface,
+and so all must be overridden in subclasses.
+
+\begin{methoddesc}[Request]{add_data}{data}
+Set the \class{Request} data to \var{data} is ignored
+by all handlers except HTTP handlers --- and there it should be an
+\code{application/x-www-form-encoded} buffer, and will change the
+request to be \code{POST} rather then \code{GET}.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{has_data}{data}
+Return whether the instance has a non-\code{None} data.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{get_data}{data}
+Return the instance's data.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{add_header}{key, val}
+Add another header to the request. Headers
+are currently ignored by all handlers except HTTP handlers, where they
+are added to the list of headers sent to the server. Note that there
+cannot be more then one header with the same name, and later calls
+will overwrite previous calls in case the \var{key} collides. Currently,
+this is no loss of HTTP functionality, since all headers which have meaning
+when used more then once have a (header-specific) way of gaining the
+same functionality using only one header.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{get_full_url}{}
+Return the URL given in the constructor.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{get_type}{}
+Return the type of the URL --- also known as the schema.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{get_host}{}
+Return the host to which connection will be made.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{get_selector}{}
+Return the selector --- the part of the URL that is sent to
+the server.
+\end{methoddesc}
+
+\begin{methoddesc}[Request]{set_proxy}{host, type}
+Make the request by connecting to a proxy server. The \var{host} and \var{type}
+will replace those of the instance, and the instance's selector will be
+the original URL given in the constructor.
+\end{methoddesc}
+
+\begin{classdesc}{OpenerDirector}{}
+The \class{OpenerDirector} class opens URLs via \class{BaseHandler}s chained
+together. It manages the chaining of handlers, and recovery from errors.
+\end{classdesc}
+
+\begin{methoddesc}[OpenerDirector]{add_handler}{handler}
+\var{handler} should be an instance of \class{BaseHandler}. The following
+methods are searched, and added to the possible chains.
+
+\begin{itemize}
+ \item \code{{\em protocol}_open} --- signal that the handler knows how
+ to open {\em protocol} URLs.
+ \item \code{{\em protocol}_error_{\em type}} -- signal that the handler
+ knows how to handle {\em type}
+ errors from {\em protocol}.
+\end{itemize}
+
+\end{methoddesc}
+
+\begin{methoddesc}[OpenerDirector]{close}{}
+Explicitly break cycles, and delete all the handlers.
+Because the \class{OpenerDirector} needs to know the registered handlers,
+and a handler needs to know who the \class{OpenerDirector} who called
+it is, there is a reference cycles. Even though recent versions of Python
+have cycle-collection, it is sometimes preferable to explicitly break
+the cycles.
+\end{methoddesc}
+
+\begin{methoddesc}[OpenerDirector]{open}{url\optional{, data}}
+Open the given \var{url}. (which can be a request object or a string),
+optionally passing the given \var{data}.
+Arguments, return values and exceptions raised are the same as those
+of \function{urlopen} (which simply calls the \method{open()} method
+on the default installed \class{OpenerDirector}.
+\end{methoddesc}
+
+\begin{methoddesc}[OpenerDirector]{error}{proto\optional{, arg\optional{, ...}}}
+Handle an error in a given protocol. The HTTP protocol is special cased to
+use the code as the error. This will call the registered error handlers
+for the given protocol with the given arguments (which are protocol specific).
+
+Return values and exceptions raised are the same as those
+of \function{urlopen}.
+\end{methoddesc}
+
+\begin{classdesc}{BaseHandler}{}
+This is the base class for all registered handlers --- and handles only
+the simple mechanics of registration.
+\end{classdesc}
+
+\begin{methoddesc}[BaseHandler]{add_parent}{director}
+Add a director as parent.
+\end{methoddesc}
+
+\begin{methoddesc}[BaseHandler]{close}{}
+Remove any parents.
+\end{methoddesc}
+
+The following members and methods should be used only be classes derived
+from \class{BaseHandler}:
+
+\begin{memberdesc}[BaseHandler]{parent}
+A valid \class{OpenerDirector}, which can be used to open using a different
+protocol, or handle errors.
+\end{memberdesc}
+
+\begin{methoddesc}[BaseHandler]{default_open}{req}
+This method is {\em not} defined in \class{BaseHandler}, but subclasses
+should define it if they want to catch all URLs.
+
+This method, if exists, will be called by the \member{parent}
+\class{OpenerDirector}. It should return a file-like object as described
+in the return value of the \method{open} of \class{OpenerDirector} or
+\code{None}. It should raise \exception{URLError}, unless a truly exceptional
+thing happens (for example, \exception{MemoryError} should not be mapped
+to \exception{URLError}.
+
+This method will be called before any protocol-specific open method.
+\end{methoddesc}
+
+\begin{methoddesc}[BaseHandler]{{\em protocol}_open}{req}
+This method is {\em not} defined in \class{BaseHandler}, but subclasses
+should define it if they want to handle URLs with the given protocol.
+
+This method, if exists, will be called by the \member{parent}
+\class{OpenerDirector}. Return values should be the same as for
+\method{default_open}.
+\end{methoddesc}
+
+\begin{methoddesc}[BaseHandler]{unknown_open}{req}
+This method is {\em not} defined in \class{BaseHandler}, but subclasses
+should define it if they want to catch all URLs with no specific
+registerd handler to open it.
+
+This method, if exists, will be called by the \member{parent}
+\class{OpenerDirector}. Return values should be the same as for
+\method{default_open}.
+\end{methoddesc}
+
+\begin{methoddesc}[BaseHandler]{http_error_default}{req, fp, code, msg, hdrs}
+This method is {\em not} defined in \class{BaseHandler}, but subclasses
+should override it if they intend to provide a catch-all for otherwise
+unhandled HTTP errors. It will be called automatically by the
+\class{OpenerDirector} getting the error, and should not normally be called
+in other circumstances.
+
+\var{req} will be a \class{Request} object, \var{fp} will be a file-like
+object with the HTTP error body, \var{code} will be the three-digit code
+of the error, \var{msg} will be the user-visible explanation of the
+code and \var{hdrs} will be a dictionary-like object with the headers of
+the error.
+
+Return values and exceptions raised should be the same as those
+of \function{urlopen}.
+\end{methoddesc}
+
+\begin{methoddesc}[BaseHandler]{http_error_{\em nnn}}{req, fp, code, msg, hdrs}
+\code{nnn} should be a three-digit HTTP error code. This method is also
+not defined in \class{BaseHandler}, but will be called, if it exists, on
+an instance of a subclass, when an HTTP error with code \code{nnn} occurse.
+
+Subclasses should override this method to handle specific HTTP errors.
+
+Arguments, return values and exceptions raised shoudl be the same as for
+\method{http_error_default}
+\end{methoddesc}
+
+
+\begin{classdesc}{HTTPDefaultErrorHandler}{}
+A class which catches all HTTP errors.
+\end{classdesc}
+
+\begin{methoddesc}[HTTPDefaultErrorHandler]{http_error_default}{req, fp, code,
+ msg, hdrs}
+Raise an \exception{HTTPError}
+\end{methoddesc}
+
+\begin{classdesc}{HTTPRedirectHandler}{}
+A class to handle redirections.
+\end{classdesc}
+
+\begin{methoddesc}[HTTPRedirectHandler]{http_error_301}{req, fp, code,
+ msg, hdrs}
+Redirect to the \code{Location:} URL. This method gets called by
+the parent \class{OpenerDirector} when getting an HTTP permanent-redirect
+error.
+\end{methoddesc}
+
+\begin{methoddesc}[HTTPRedirectHandler]{http_error_302}{req, fp, code,
+ msg, hdrs}
+The same as \method{http_error_301}.
+\end{methoddesc}
+
+\strong{Note:} 303 redirection is not supported by this version of
+\module{urllib2}.
+
+\begin{classdesc}{ProxyHandler}{\optional{proxies}}
+Cause requests to go through a proxy.
+If \var{proxies} is given, it must be a dictionary mapping
+protocol names to URLs of proxies.
+The default is to read the list of proxies from the environment
+variables \code{{\em protocol}_proxy}.
+\end{classdesc}
+
+\begin{methoddesc}[ProxyHandler]{{\em protocol}_open}{request}
+The \class{ProxyHandler} will have a method \code{{\em protocol}_open} for
+every {\em protocol} which has a proxy in the \var{proxies} dictionary
+given in the constructor. The method will modify requests to go
+through the proxy, by calling \code{request.set_proxy()}, and call the next
+handler in the chain to actually execute the protocol.
+\end{methoddesc}
+
+\begin{classdesc}{HTTPPasswordMgr}{}
+Keep a database of
+\code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})} mapping.
+\end{classdesc}
+
+\begin{methoddesc}[HTTPPasswordMgr]{add_password}{realm, uri, user, passwd}
+\var{uri} can be either a single URI, or a sequene of URIs. \var{realm},
+\var{user} and \var{passwd} must be strings. This causes
+ \code{(\var{user}, \var{passwd})} to be used as authentication tokens
+when authentication for \var{realm} and a super-URI of any of the
+given URIs is given.
+\end{methoddesc}
+
+\begin{methoddesc}[HTTPPasswordMgr]{find_user_password}{realm, authuri}
+Get user/password for given realm and URI, if any. This method will
+return \code{(None, None)} if there is no user/password is known.
+\end{methoddesc}
+
+\begin{classdesc}{HTTPPasswordMgrWithDefaultRealm}{}
+Keep a database of
+\code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})} mapping.
+A realm of \code{None} is considered a catch-all realm, which is searched
+if no other realm fits.
+\end{classdesc}
+
+\begin{methoddesc}[HTTPPasswordMgrWithDefaultRealm]{add_password}
+ {realm, uri, user, passwd}
+\var{uri} can be either a single URI, or a sequene of URIs. \var{realm},
+\var{user} and \var{passwd} must be strings. This causes
+ \code{(\var{user}, \var{passwd})} to be used as authentication tokens
+when authentication for \var{realm} and a super-URI of any of the
+given URIs is given.
+\end{methoddesc}
+
+\begin{methoddesc}[HTTPPasswordMgr]{find_user_password}{realm, authuri}
+Get user/password for given realm and URI, if any. This method will
+return \code{(None, None)} if there is no user/password is known.
+If the given \var{realm} has no user/password, the realm \code{None}
+will be searched.
+\end{methoddesc}
+
+\begin{classdesc}[AbstractBasicAuthHandler]{\optional{password_mgr}}
+This is a mixin class, that helps with HTTP authentication, both
+to the remote host and to a proxy.
+
+\var{password_mgr} should be something that is compatible with
+\class{HTTPPasswordMgr} --- supplies the documented interface above.
+\end{classdesc}
+
+\begin{methoddesc}[AbstractBasicAuthHandler]{handle_authentication_request}
+ {authreq, host, req, headers}
+Handle an authentication request by getting user/password pair, and retrying.
+\var{authreq} should be the name of the header where the information about
+the realm, \var{host} is the host to authenticate too, \var{req} should be the
+(failed) \class{Request} object, and \var{headers} should be the error headers.
+\end{methoddesc}
+
+\begin{classdesc}{HTTPBasicAuthHandler}{\optional{password_mgr}}
+Handle authentication with the remote host.
+Valid \var{password_mgr}, if given, are the same as for
+\class{AbstractBasicAuthHandler}.
+\end{classdesc}
+
+\begin{methoddesc}[HTTPBasicAuthHandler]{http_error_401}{req, fp, code,
+ msg, hdrs}
+Retry the request with authentication info, if available.
+\end{methoddesc}
+
+\begin{classdesc}{ProxyBasicAuthHandler}{\optional{password_mgr}}
+Handle authentication with the proxy.
+Valid \var{password_mgr}, if given, are the same as for
+\class{AbstractBasicAuthHandler}.
+\end{classdesc}
+
+\begin{methoddesc}[ProxyBasicAuthHandler]{http_error_407}{req, fp, code,
+ msg, hdrs}
+Retry the request with authentication info, if available.
+\end{methoddesc}
+
+\begin{classdesc}{AbstractDigestAuthHandler}{\optional{password_mgr}}
+This is a mixin class, that helps with HTTP authentication, both
+to the remote host and to a proxy.
+
+\var{password_mgr} should be something that is compatible with
+\class{HTTPPasswordMgr} --- supplies the documented interface above.
+\end{classdesc}
+
+\begin{methoddesc}[AbstractBasicAuthHandler]{handle_authentication_request}
+ {authreq, host, req, headers}
+\var{authreq} should be the name of the header where the information about
+the realm, \var{host} should be the host to authenticate too, \var{req}
+should be the (failed) \class{Request} object, and \var{headers} should be the
+error headers.
+\end{methoddesc}
+
+\begin{classdesc}{HTTPDigestAuthHandler}{\optional{password_mgr}}
+Handle authentication with the remote host.
+Valid \var{password_mgr}, if given, are the same as for
+\class{AbstractBasicAuthHandler}.
+\end{classdesc}
+
+\begin{methoddesc}[HTTPDigestAuthHandler]{http_error_401}{req, fp, code,
+ msg, hdrs}
+Retry the request with authentication info, if available.
+\end{methoddesc}
+
+\begin{classdesc}{ProxyDigestAuthHandler}{\optional{password_mgr}}
+Handle authentication with the proxy.
+\var{password_mgr}, if given, shoudl be the same as for
+the constructor of \class{AbstractDigestAuthHandler}.
+\end{classdesc}
+
+\begin{methoddesc}[ProxyDigestAuthHandler]{http_error_407}{req, fp, code,
+ msg, hdrs}
+Retry the request with authentication info, if available.
+\end{methoddesc}
+
+\begin{classdesc}{HTTPHandler}{}
+A class to handle opening of HTTP URLs
+\end{classdesc}
+
+\begin{methoddesc}[HTTPHandler]{http_open}{req}
+Send an HTTP request (either GET or POST, depending on whether
+\code{req.has_data()}.
+\end{methoddesc}
+
+\begin{classdesc}{HTTPSHandler}{}
+A class to handle opening of HTTPS URLs
+\end{classdesc}
+
+\begin{methoddesc}[HTTPSHandler]{https_open}{req}
+Send an HTTPS request (either GET or POST, depending on whether
+\code{req.has_data()}.
+\end{methoddesc}
+
+\begin{classdesc}{UknownHandler}{}
+A catch-all class to handle unknown URLs.
+\end{classdesc}
+
+\begin{methoddesc}[UknownHandler]{unknown_open}
+Raise a \exception{URLError} exception
+\end{methoddesc}
+
+\begin{classdesc}{FileHandler}{}
+Open local files.
+\end{classdesc}
+
+\begin{methoddesc}[FileHandler]{file_open}{req}
+Open the file locally, if there is no host name, or
+the host name is \code{"localhost"}. Change the
+protocol to \code{ftp} otherwise, and retry opening
+it using \member{parent}.
+\end{methoddesc}
+
+\begin{classdesc}{FTPHandler}{}
+Open FTP URLs.
+\end{classdesc}
+
+\begin{methoddesc}[FTPHandler]{ftp_open}{req}
+Open the FTP file indicated by \var{req}.
+The login is always done with empty username and password.
+\end{methoddesc}
+
+\begin{classdesc}{CacheFTPHandler}{}
+Open FTP URLs, keeping a cache of open FTP connections to minimize
+delays.
+\end{classdesc}
+
+\begin{methoddesc}[CacheFTPHandler]{ftp_open}{req}
+Open the FTP file indicated by \var{req}.
+The login is always done with empty username and password.
+\end{methoddesc}
+
+\begin{methoddesc}[CacheFTPHandler]{setTimeout}{t}
+Set timeout of connections to \var{t} seconds.
+\end{methoddesc}
+
+\begin{methoddesc}[CacheFTPHandler]{setMaxConns}{m}
+Set maximum number of cached connections to \var{m}.
+\end{methoddesc}
+
+\begin{classdesc}{GopherHandler}{}
+Open gopher URLs.
+\end{classdesc}
+
+\begin{methoddesc}[GopherHandler]{gopher_open}{req}
+Open the gopher resource indicated by \var{req}.
+\end{methoddesc}