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8a18e99008
(please not that the library reference does *not* include the urllib2 documnetation -- that will wiat for Fred)
501 lines
19 KiB
TeX
501 lines
19 KiB
TeX
\section{\module{urllib2} ---
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extensible library for opening URLs}
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\declaremodule{standard}{urllib2}
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\moduleauthor{Jeremy Hylton}{jhylton@users.sourceforge.net}
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\sectionauthor{Moshe Zadka}{moshez@users.sourceforge.net}
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\modulesynopsis{An extensible library for opening URLs using a variety of
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protocols}
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The \module{urllib2} module defines functions and classes which help
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in opening URLs (mostly HTTP) in a complex world -- basic and digest
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authentication, redirections and more.
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The \module{urllib2} module defines the following functions:
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\begin{funcdesc}{urlopen}{url\optional{, data}}
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Open the url \var{url}, which can either a string or a \class{Request}
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object (currently the code checks that it really is a \class{Request}
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instance, or an instance of a subclass of \class{Request}.
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\var{data} should be a string, which specifies additional data to
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send to the server. In HTTP requests, which are the only ones that
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support \var{data}, it should be a buffer in the format of
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\code{application/x-www-form-urlencoded}, for example one returned
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from \function{urllib.urlencode}.
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This function returns a file-like object with two additional methods:
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\begin{itemize}
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\item \code{geturl()} --- return the URL of the resource retrieved
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\item \code{info()} --- return the meta-information of the page, as
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a dictionary-like object
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\end{itemize}
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Raises \exception{URLError} on errors.
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\end{funcdesc}
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\begin{funcdesc}{install_opener}{opener}
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Install a \class{OpenerDirector} instance as the default opener.
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The code does not check for a real \class{OpenerDirector}, and any
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class with the appropriate interface will work.
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\end{funcdesc}
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\begin{funcdesc}{build_opener}{\optional{handler\optional{,
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handler\optional{, ...}}}}
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Return an \class{OpenerDirector} instance, which chains the
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handlers in the order given. \var{handler}s can be either instances
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of \class{BaseHandler}, or subclasses of \class{BaseHandler} (in
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which case it must be possible to call the constructor without
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any parameters. Instances of the following classes will be in
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the front of the \var{handler}s, unless the \var{handler}s contain
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them, instances of them or subclasses of them:
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\code{ProxyHandler, UnknownHandler, HTTPHandler, HTTPDefaultErrorHandler,
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HTTPRedirectHandler, FTPHandler, FileHandler}
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If the Python installation has SSL support (\code{socket.ssl} exists),
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\class{HTTPSHandler} will also be added.
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\end{funcdesc}
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\begin{excdesc}{URLError}
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The error handlers raise when they run into a problem. It is a subclass
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of \exception{IOError}.
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\end{excdesc}
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\begin{excdesc}{HTTPError}
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A subclass of \exception{URLError}, it can also function as a
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non-exceptional file-like return value (the same thing that \function{urlopen}
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returns). This is useful when handling exotic HTTP errors, such as
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requests for authentications.
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\end{excdesc}
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\begin{excdesc}{GopherError}
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A subclass of \exception{URLError}, this is the error raised by the
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Gopher handler.
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\end{excdesc}
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\begin{classdesc}{Request}{url\optional{data, \optional{, headers}}}
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This class is an abstraction of a URL request.
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\var{url} should be a string which is a valid URL. For descrtion
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of \var{data} see the \method{add_data} description.
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\var{headers} should be a dictionary, and will be treated as if
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\method{add_header} was called with each key and value as arguments.
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\end{classdesc}
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The following methods describe all of \class{Request}'s public interface,
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and so all must be overridden in subclasses.
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\begin{methoddesc}[Request]{add_data}{data}
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Set the \class{Request} data to \var{data} is ignored
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by all handlers except HTTP handlers --- and there it should be an
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\code{application/x-www-form-encoded} buffer, and will change the
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request to be \code{POST} rather then \code{GET}.
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\end{methoddesc}
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\begin{methoddesc}[Request]{has_data}{data}
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Return whether the instance has a non-\code{None} data.
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\end{methoddesc}
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\begin{methoddesc}[Request]{get_data}{data}
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Return the instance's data.
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\end{methoddesc}
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\begin{methoddesc}[Request]{add_header}{key, val}
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Add another header to the request. Headers
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are currently ignored by all handlers except HTTP handlers, where they
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are added to the list of headers sent to the server. Note that there
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cannot be more then one header with the same name, and later calls
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will overwrite previous calls in case the \var{key} collides. Currently,
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this is no loss of HTTP functionality, since all headers which have meaning
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when used more then once have a (header-specific) way of gaining the
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same functionality using only one header.
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\end{methoddesc}
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\begin{methoddesc}[Request]{get_full_url}{}
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Return the URL given in the constructor.
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\end{methoddesc}
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\begin{methoddesc}[Request]{get_type}{}
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Return the type of the URL --- also known as the schema.
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\end{methoddesc}
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\begin{methoddesc}[Request]{get_host}{}
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Return the host to which connection will be made.
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\end{methoddesc}
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\begin{methoddesc}[Request]{get_selector}{}
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Return the selector --- the part of the URL that is sent to
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the server.
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\end{methoddesc}
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\begin{methoddesc}[Request]{set_proxy}{host, type}
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Make the request by connecting to a proxy server. The \var{host} and \var{type}
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will replace those of the instance, and the instance's selector will be
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the original URL given in the constructor.
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\end{methoddesc}
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\begin{classdesc}{OpenerDirector}{}
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The \class{OpenerDirector} class opens URLs via \class{BaseHandler}s chained
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together. It manages the chaining of handlers, and recovery from errors.
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\end{classdesc}
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\begin{methoddesc}[OpenerDirector]{add_handler}{handler}
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\var{handler} should be an instance of \class{BaseHandler}. The following
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methods are searched, and added to the possible chains.
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\begin{itemize}
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\item \code{{\em protocol}_open} --- signal that the handler knows how
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to open {\em protocol} URLs.
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\item \code{{\em protocol}_error_{\em type}} -- signal that the handler
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knows how to handle {\em type}
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errors from {\em protocol}.
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\end{itemize}
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\end{methoddesc}
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\begin{methoddesc}[OpenerDirector]{close}{}
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Explicitly break cycles, and delete all the handlers.
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Because the \class{OpenerDirector} needs to know the registered handlers,
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and a handler needs to know who the \class{OpenerDirector} who called
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it is, there is a reference cycles. Even though recent versions of Python
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have cycle-collection, it is sometimes preferable to explicitly break
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the cycles.
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\end{methoddesc}
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\begin{methoddesc}[OpenerDirector]{open}{url\optional{, data}}
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Open the given \var{url}. (which can be a request object or a string),
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optionally passing the given \var{data}.
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Arguments, return values and exceptions raised are the same as those
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of \function{urlopen} (which simply calls the \method{open()} method
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on the default installed \class{OpenerDirector}.
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\end{methoddesc}
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\begin{methoddesc}[OpenerDirector]{error}{proto\optional{, arg\optional{, ...}}}
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Handle an error in a given protocol. The HTTP protocol is special cased to
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use the code as the error. This will call the registered error handlers
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for the given protocol with the given arguments (which are protocol specific).
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Return values and exceptions raised are the same as those
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of \function{urlopen}.
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\end{methoddesc}
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\begin{classdesc}{BaseHandler}{}
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This is the base class for all registered handlers --- and handles only
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the simple mechanics of registration.
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\end{classdesc}
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\begin{methoddesc}[BaseHandler]{add_parent}{director}
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Add a director as parent.
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\end{methoddesc}
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\begin{methoddesc}[BaseHandler]{close}{}
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Remove any parents.
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\end{methoddesc}
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The following members and methods should be used only be classes derived
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from \class{BaseHandler}:
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\begin{memberdesc}[BaseHandler]{parent}
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A valid \class{OpenerDirector}, which can be used to open using a different
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protocol, or handle errors.
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\end{memberdesc}
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\begin{methoddesc}[BaseHandler]{default_open}{req}
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This method is {\em not} defined in \class{BaseHandler}, but subclasses
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should define it if they want to catch all URLs.
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This method, if exists, will be called by the \member{parent}
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\class{OpenerDirector}. It should return a file-like object as described
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in the return value of the \method{open} of \class{OpenerDirector} or
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\code{None}. It should raise \exception{URLError}, unless a truly exceptional
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thing happens (for example, \exception{MemoryError} should not be mapped
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to \exception{URLError}.
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This method will be called before any protocol-specific open method.
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\end{methoddesc}
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\begin{methoddesc}[BaseHandler]{{\em protocol}_open}{req}
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This method is {\em not} defined in \class{BaseHandler}, but subclasses
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should define it if they want to handle URLs with the given protocol.
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This method, if exists, will be called by the \member{parent}
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\class{OpenerDirector}. Return values should be the same as for
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\method{default_open}.
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\end{methoddesc}
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\begin{methoddesc}[BaseHandler]{unknown_open}{req}
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This method is {\em not} defined in \class{BaseHandler}, but subclasses
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should define it if they want to catch all URLs with no specific
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registerd handler to open it.
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This method, if exists, will be called by the \member{parent}
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\class{OpenerDirector}. Return values should be the same as for
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\method{default_open}.
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\end{methoddesc}
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\begin{methoddesc}[BaseHandler]{http_error_default}{req, fp, code, msg, hdrs}
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This method is {\em not} defined in \class{BaseHandler}, but subclasses
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should override it if they intend to provide a catch-all for otherwise
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unhandled HTTP errors. It will be called automatically by the
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\class{OpenerDirector} getting the error, and should not normally be called
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in other circumstances.
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\var{req} will be a \class{Request} object, \var{fp} will be a file-like
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object with the HTTP error body, \var{code} will be the three-digit code
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of the error, \var{msg} will be the user-visible explanation of the
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code and \var{hdrs} will be a dictionary-like object with the headers of
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the error.
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Return values and exceptions raised should be the same as those
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of \function{urlopen}.
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\end{methoddesc}
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\begin{methoddesc}[BaseHandler]{http_error_{\em nnn}}{req, fp, code, msg, hdrs}
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\code{nnn} should be a three-digit HTTP error code. This method is also
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not defined in \class{BaseHandler}, but will be called, if it exists, on
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an instance of a subclass, when an HTTP error with code \code{nnn} occurse.
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Subclasses should override this method to handle specific HTTP errors.
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Arguments, return values and exceptions raised shoudl be the same as for
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\method{http_error_default}
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\end{methoddesc}
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\begin{classdesc}{HTTPDefaultErrorHandler}{}
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A class which catches all HTTP errors.
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\end{classdesc}
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\begin{methoddesc}[HTTPDefaultErrorHandler]{http_error_default}{req, fp, code,
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msg, hdrs}
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Raise an \exception{HTTPError}
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\end{methoddesc}
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\begin{classdesc}{HTTPRedirectHandler}{}
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A class to handle redirections.
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\end{classdesc}
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\begin{methoddesc}[HTTPRedirectHandler]{http_error_301}{req, fp, code,
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msg, hdrs}
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Redirect to the \code{Location:} URL. This method gets called by
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the parent \class{OpenerDirector} when getting an HTTP permanent-redirect
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error.
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\end{methoddesc}
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\begin{methoddesc}[HTTPRedirectHandler]{http_error_302}{req, fp, code,
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msg, hdrs}
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The same as \method{http_error_301}.
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\end{methoddesc}
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\strong{Note:} 303 redirection is not supported by this version of
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\module{urllib2}.
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\begin{classdesc}{ProxyHandler}{\optional{proxies}}
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Cause requests to go through a proxy.
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If \var{proxies} is given, it must be a dictionary mapping
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protocol names to URLs of proxies.
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The default is to read the list of proxies from the environment
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variables \code{{\em protocol}_proxy}.
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\end{classdesc}
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\begin{methoddesc}[ProxyHandler]{{\em protocol}_open}{request}
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The \class{ProxyHandler} will have a method \code{{\em protocol}_open} for
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every {\em protocol} which has a proxy in the \var{proxies} dictionary
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given in the constructor. The method will modify requests to go
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through the proxy, by calling \code{request.set_proxy()}, and call the next
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handler in the chain to actually execute the protocol.
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\end{methoddesc}
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\begin{classdesc}{HTTPPasswordMgr}{}
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Keep a database of
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\code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})} mapping.
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\end{classdesc}
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\begin{methoddesc}[HTTPPasswordMgr]{add_password}{realm, uri, user, passwd}
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\var{uri} can be either a single URI, or a sequene of URIs. \var{realm},
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\var{user} and \var{passwd} must be strings. This causes
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\code{(\var{user}, \var{passwd})} to be used as authentication tokens
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when authentication for \var{realm} and a super-URI of any of the
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given URIs is given.
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\end{methoddesc}
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\begin{methoddesc}[HTTPPasswordMgr]{find_user_password}{realm, authuri}
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Get user/password for given realm and URI, if any. This method will
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return \code{(None, None)} if there is no user/password is known.
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\end{methoddesc}
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\begin{classdesc}{HTTPPasswordMgrWithDefaultRealm}{}
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Keep a database of
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\code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})} mapping.
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A realm of \code{None} is considered a catch-all realm, which is searched
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if no other realm fits.
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\end{classdesc}
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\begin{methoddesc}[HTTPPasswordMgrWithDefaultRealm]{add_password}
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{realm, uri, user, passwd}
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\var{uri} can be either a single URI, or a sequene of URIs. \var{realm},
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\var{user} and \var{passwd} must be strings. This causes
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\code{(\var{user}, \var{passwd})} to be used as authentication tokens
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when authentication for \var{realm} and a super-URI of any of the
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given URIs is given.
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\end{methoddesc}
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\begin{methoddesc}[HTTPPasswordMgr]{find_user_password}{realm, authuri}
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Get user/password for given realm and URI, if any. This method will
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return \code{(None, None)} if there is no user/password is known.
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If the given \var{realm} has no user/password, the realm \code{None}
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will be searched.
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\end{methoddesc}
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\begin{classdesc}[AbstractBasicAuthHandler]{\optional{password_mgr}}
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This is a mixin class, that helps with HTTP authentication, both
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to the remote host and to a proxy.
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\var{password_mgr} should be something that is compatible with
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\class{HTTPPasswordMgr} --- supplies the documented interface above.
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\end{classdesc}
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\begin{methoddesc}[AbstractBasicAuthHandler]{handle_authentication_request}
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{authreq, host, req, headers}
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Handle an authentication request by getting user/password pair, and retrying.
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\var{authreq} should be the name of the header where the information about
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the realm, \var{host} is the host to authenticate too, \var{req} should be the
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(failed) \class{Request} object, and \var{headers} should be the error headers.
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\end{methoddesc}
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\begin{classdesc}{HTTPBasicAuthHandler}{\optional{password_mgr}}
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Handle authentication with the remote host.
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Valid \var{password_mgr}, if given, are the same as for
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\class{AbstractBasicAuthHandler}.
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\end{classdesc}
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\begin{methoddesc}[HTTPBasicAuthHandler]{http_error_401}{req, fp, code,
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msg, hdrs}
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Retry the request with authentication info, if available.
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\end{methoddesc}
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\begin{classdesc}{ProxyBasicAuthHandler}{\optional{password_mgr}}
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Handle authentication with the proxy.
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Valid \var{password_mgr}, if given, are the same as for
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\class{AbstractBasicAuthHandler}.
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\end{classdesc}
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\begin{methoddesc}[ProxyBasicAuthHandler]{http_error_407}{req, fp, code,
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msg, hdrs}
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Retry the request with authentication info, if available.
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\end{methoddesc}
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\begin{classdesc}{AbstractDigestAuthHandler}{\optional{password_mgr}}
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This is a mixin class, that helps with HTTP authentication, both
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to the remote host and to a proxy.
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\var{password_mgr} should be something that is compatible with
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\class{HTTPPasswordMgr} --- supplies the documented interface above.
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\end{classdesc}
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\begin{methoddesc}[AbstractBasicAuthHandler]{handle_authentication_request}
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{authreq, host, req, headers}
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\var{authreq} should be the name of the header where the information about
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the realm, \var{host} should be the host to authenticate too, \var{req}
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should be the (failed) \class{Request} object, and \var{headers} should be the
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error headers.
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\end{methoddesc}
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\begin{classdesc}{HTTPDigestAuthHandler}{\optional{password_mgr}}
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Handle authentication with the remote host.
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Valid \var{password_mgr}, if given, are the same as for
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\class{AbstractBasicAuthHandler}.
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\end{classdesc}
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\begin{methoddesc}[HTTPDigestAuthHandler]{http_error_401}{req, fp, code,
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msg, hdrs}
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Retry the request with authentication info, if available.
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\end{methoddesc}
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\begin{classdesc}{ProxyDigestAuthHandler}{\optional{password_mgr}}
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Handle authentication with the proxy.
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\var{password_mgr}, if given, shoudl be the same as for
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the constructor of \class{AbstractDigestAuthHandler}.
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\end{classdesc}
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\begin{methoddesc}[ProxyDigestAuthHandler]{http_error_407}{req, fp, code,
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msg, hdrs}
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Retry the request with authentication info, if available.
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\end{methoddesc}
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\begin{classdesc}{HTTPHandler}{}
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A class to handle opening of HTTP URLs
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\end{classdesc}
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\begin{methoddesc}[HTTPHandler]{http_open}{req}
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Send an HTTP request (either GET or POST, depending on whether
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\code{req.has_data()}.
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\end{methoddesc}
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\begin{classdesc}{HTTPSHandler}{}
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A class to handle opening of HTTPS URLs
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\end{classdesc}
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\begin{methoddesc}[HTTPSHandler]{https_open}{req}
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Send an HTTPS request (either GET or POST, depending on whether
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\code{req.has_data()}.
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\end{methoddesc}
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\begin{classdesc}{UknownHandler}{}
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A catch-all class to handle unknown URLs.
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\end{classdesc}
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\begin{methoddesc}[UknownHandler]{unknown_open}
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Raise a \exception{URLError} exception
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\end{methoddesc}
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\begin{classdesc}{FileHandler}{}
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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}
|