Documentation updates for urllib package. Modified the documentation for the
urllib,urllib2 -> urllib.request,urllib.error
urlparse -> urllib.parse
RobotParser -> urllib.robotparser
Updated tutorial references and other module references (http.client.rst,
ftplib.rst,contextlib.rst)
Updated the examples in the urllib2-howto
Addresses Issue3142.
diff --git a/Doc/library/urllib.request.rst b/Doc/library/urllib.request.rst
new file mode 100644
index 0000000..4262836
--- /dev/null
+++ b/Doc/library/urllib.request.rst
@@ -0,0 +1,1194 @@
+:mod:`urllib.request` --- extensible library for opening URLs
+=============================================================
+
+.. module:: urllib.request
+ :synopsis: Next generation URL opening library.
+.. moduleauthor:: Jeremy Hylton <jhylton@users.sourceforge.net>
+.. sectionauthor:: Moshe Zadka <moshez@users.sourceforge.net>
+
+
+The :mod:`urllib.request` module defines functions and classes which help in opening
+URLs (mostly HTTP) in a complex world --- basic and digest authentication,
+redirections, cookies and more.
+
+The :mod:`urllib.request` module defines the following functions:
+
+
+.. function:: urlopen(url[, data][, timeout])
+
+ Open the URL *url*, which can be either a string or a :class:`Request` object.
+
+ *data* may be a string specifying additional data to send to the server, or
+ ``None`` if no such data is needed. Currently HTTP requests are the only ones
+ that use *data*; the HTTP request will be a POST instead of a GET when the
+ *data* parameter is provided. *data* should be a buffer in the standard
+ :mimetype:`application/x-www-form-urlencoded` format. The
+ :func:`urllib.urlencode` function takes a mapping or sequence of 2-tuples and
+ returns a string in this format.
+
+ The optional *timeout* parameter specifies a timeout in seconds for blocking
+ operations like the connection attempt (if not specified, the global default
+ timeout setting will be used). This actually only works for HTTP, HTTPS,
+ FTP and FTPS connections.
+
+ This function returns a file-like object with two additional methods from
+ the :mod:`urllib.response` module
+
+ * :meth:`geturl` --- return the URL of the resource retrieved, commonly used to
+ determine if a redirect was followed
+
+ * :meth:`info` --- return the meta-information of the page, such as headers, in
+ the form of an ``http.client.HTTPMessage`` instance
+ (see `Quick Reference to HTTP Headers <http://www.cs.tut.fi/~jkorpela/http.html>`_)
+
+ Raises :exc:`URLError` on errors.
+
+ Note that ``None`` may be returned if no handler handles the request (though the
+ default installed global :class:`OpenerDirector` uses :class:`UnknownHandler` to
+ ensure this never happens).
+ The urlopen function from the previous version, Python 2.6 and earlier, of
+ the module urllib has been discontinued as urlopen can return the
+ file-object as the previous. The proxy handling, which in earlier was passed
+ as a dict parameter to urlopen can be availed by the use of `ProxyHandler`
+ objects.
+
+
+.. function:: install_opener(opener)
+
+ Install an :class:`OpenerDirector` instance as the default global opener.
+ Installing an opener is only necessary if you want urlopen to use that opener;
+ otherwise, simply call :meth:`OpenerDirector.open` instead of :func:`urlopen`.
+ The code does not check for a real :class:`OpenerDirector`, and any class with
+ the appropriate interface will work.
+
+
+.. function:: build_opener([handler, ...])
+
+ Return an :class:`OpenerDirector` instance, which chains the handlers in the
+ order given. *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 front of the *handler*\s, unless the *handler*\s contain them,
+ instances of them or subclasses of them: :class:`ProxyHandler`,
+ :class:`UnknownHandler`, :class:`HTTPHandler`, :class:`HTTPDefaultErrorHandler`,
+ :class:`HTTPRedirectHandler`, :class:`FTPHandler`, :class:`FileHandler`,
+ :class:`HTTPErrorProcessor`.
+
+ If the Python installation has SSL support (i.e., if the :mod:`ssl` module can be imported),
+ :class:`HTTPSHandler` will also be added.
+
+ A :class:`BaseHandler` subclass may also change its :attr:`handler_order`
+ member variable to modify its position in the handlers list.
+
+.. function:: urlretrieve(url[, filename[, reporthook[, data]]])
+
+ Copy a network object denoted by a URL to a local file, if necessary. If the URL
+ points to a local file, or a valid cached copy of the object exists, the object
+ is not copied. Return a tuple ``(filename, headers)`` where *filename* is the
+ local file name under which the object can be found, and *headers* is whatever
+ the :meth:`info` method of the object returned by :func:`urlopen` returned (for
+ a remote object, possibly cached). Exceptions are the same as for
+ :func:`urlopen`.
+
+ The second argument, if present, specifies the file location to copy to (if
+ absent, the location will be a tempfile with a generated name). The third
+ argument, if present, is a hook function that will be called once on
+ establishment of the network connection and once after each block read
+ thereafter. The hook will be passed three arguments; a count of blocks
+ transferred so far, a block size in bytes, and the total size of the file. The
+ third argument may be ``-1`` on older FTP servers which do not return a file
+ size in response to a retrieval request.
+
+ If the *url* uses the :file:`http:` scheme identifier, the optional *data*
+ argument may be given to specify a ``POST`` request (normally the request type
+ is ``GET``). The *data* argument must in standard
+ :mimetype:`application/x-www-form-urlencoded` format; see the :func:`urlencode`
+ function below.
+
+ :func:`urlretrieve` will raise :exc:`ContentTooShortError` when it detects that
+ the amount of data available was less than the expected amount (which is the
+ size reported by a *Content-Length* header). This can occur, for example, when
+ the download is interrupted.
+
+ The *Content-Length* is treated as a lower bound: if there's more data to read,
+ urlretrieve reads more data, but if less data is available, it raises the
+ exception.
+
+ You can still retrieve the downloaded data in this case, it is stored in the
+ :attr:`content` attribute of the exception instance.
+
+ If no *Content-Length* header was supplied, urlretrieve can not check the size
+ of the data it has downloaded, and just returns it. In this case you just have
+ to assume that the download was successful.
+
+
+.. data:: _urlopener
+
+ The public functions :func:`urlopen` and :func:`urlretrieve` create an instance
+ of the :class:`FancyURLopener` class and use it to perform their requested
+ actions. To override this functionality, programmers can create a subclass of
+ :class:`URLopener` or :class:`FancyURLopener`, then assign an instance of that
+ class to the ``urllib._urlopener`` variable before calling the desired function.
+ For example, applications may want to specify a different
+ :mailheader:`User-Agent` header than :class:`URLopener` defines. This can be
+ accomplished with the following code::
+
+ import urllib.request
+
+ class AppURLopener(urllib.request.FancyURLopener):
+ version = "App/1.7"
+
+ urllib._urlopener = AppURLopener()
+
+
+.. function:: urlcleanup()
+
+ Clear the cache that may have been built up by previous calls to
+ :func:`urlretrieve`.
+
+.. function:: pathname2url(path)
+
+ Convert the pathname *path* from the local syntax for a path to the form used in
+ the path component of a URL. This does not produce a complete URL. The return
+ value will already be quoted using the :func:`quote` function.
+
+
+.. function:: url2pathname(path)
+
+ Convert the path component *path* from an encoded URL to the local syntax for a
+ path. This does not accept a complete URL. This function uses :func:`unquote`
+ to decode *path*.
+
+The following classes are provided:
+
+.. class:: Request(url[, data][, headers][, origin_req_host][, unverifiable])
+
+ This class is an abstraction of a URL request.
+
+ *url* should be a string containing a valid URL.
+
+ *data* may be a string specifying additional data to send to the server, or
+ ``None`` if no such data is needed. Currently HTTP requests are the only ones
+ that use *data*; the HTTP request will be a POST instead of a GET when the
+ *data* parameter is provided. *data* should be a buffer in the standard
+ :mimetype:`application/x-www-form-urlencoded` format. The
+ :func:`urllib.urlencode` function takes a mapping or sequence of 2-tuples and
+ returns a string in this format.
+
+ *headers* should be a dictionary, and will be treated as if :meth:`add_header`
+ was called with each key and value as arguments. This is often used to "spoof"
+ the ``User-Agent`` header, which is used by a browser to identify itself --
+ some HTTP servers only allow requests coming from common browsers as opposed
+ to scripts. For example, Mozilla Firefox may identify itself as ``"Mozilla/5.0
+ (X11; U; Linux i686) Gecko/20071127 Firefox/2.0.0.11"``, while :mod:`urllib2`'s
+ default user agent string is ``"Python-urllib/2.6"`` (on Python 2.6).
+
+ The final two arguments are only of interest for correct handling of third-party
+ HTTP cookies:
+
+ *origin_req_host* should be the request-host of the origin transaction, as
+ defined by :rfc:`2965`. It defaults to ``http.cookiejar.request_host(self)``.
+ This is the host name or IP address of the original request that was
+ initiated by the user. For example, if the request is for an image in an
+ HTML document, this should be the request-host of the request for the page
+ containing the image.
+
+ *unverifiable* should indicate whether the request is unverifiable, as defined
+ by RFC 2965. It defaults to False. An unverifiable request is one whose URL
+ the user did not have the option to approve. For example, if the request is for
+ an image in an HTML document, and the user had no option to approve the
+ automatic fetching of the image, this should be true.
+
+.. class:: URLopener([proxies[, **x509]])
+
+ Base class for opening and reading URLs. Unless you need to support opening
+ objects using schemes other than :file:`http:`, :file:`ftp:`, or :file:`file:`,
+ you probably want to use :class:`FancyURLopener`.
+
+ By default, the :class:`URLopener` class sends a :mailheader:`User-Agent` header
+ of ``urllib/VVV``, where *VVV* is the :mod:`urllib` version number.
+ Applications can define their own :mailheader:`User-Agent` header by subclassing
+ :class:`URLopener` or :class:`FancyURLopener` and setting the class attribute
+ :attr:`version` to an appropriate string value in the subclass definition.
+
+ The optional *proxies* parameter should be a dictionary mapping scheme names to
+ proxy URLs, where an empty dictionary turns proxies off completely. Its default
+ value is ``None``, in which case environmental proxy settings will be used if
+ present, as discussed in the definition of :func:`urlopen`, above.
+
+ Additional keyword parameters, collected in *x509*, may be used for
+ authentication of the client when using the :file:`https:` scheme. The keywords
+ *key_file* and *cert_file* are supported to provide an SSL key and certificate;
+ both are needed to support client authentication.
+
+ :class:`URLopener` objects will raise an :exc:`IOError` exception if the server
+ returns an error code.
+
+ .. method:: open(fullurl[, data])
+
+ Open *fullurl* using the appropriate protocol. This method sets up cache and
+ proxy information, then calls the appropriate open method with its input
+ arguments. If the scheme is not recognized, :meth:`open_unknown` is called.
+ The *data* argument has the same meaning as the *data* argument of
+ :func:`urlopen`.
+
+
+ .. method:: open_unknown(fullurl[, data])
+
+ Overridable interface to open unknown URL types.
+
+
+ .. method:: retrieve(url[, filename[, reporthook[, data]]])
+
+ Retrieves the contents of *url* and places it in *filename*. The return value
+ is a tuple consisting of a local filename and either a
+ :class:`email.message.Message` object containing the response headers (for remote
+ URLs) or ``None`` (for local URLs). The caller must then open and read the
+ contents of *filename*. If *filename* is not given and the URL refers to a
+ local file, the input filename is returned. If the URL is non-local and
+ *filename* is not given, the filename is the output of :func:`tempfile.mktemp`
+ with a suffix that matches the suffix of the last path component of the input
+ URL. If *reporthook* is given, it must be a function accepting three numeric
+ parameters. It will be called after each chunk of data is read from the
+ network. *reporthook* is ignored for local URLs.
+
+ If the *url* uses the :file:`http:` scheme identifier, the optional *data*
+ argument may be given to specify a ``POST`` request (normally the request type
+ is ``GET``). The *data* argument must in standard
+ :mimetype:`application/x-www-form-urlencoded` format; see the :func:`urlencode`
+ function below.
+
+
+ .. attribute:: version
+
+ Variable that specifies the user agent of the opener object. To get
+ :mod:`urllib` to tell servers that it is a particular user agent, set this in a
+ subclass as a class variable or in the constructor before calling the base
+ constructor.
+
+
+.. class:: FancyURLopener(...)
+
+ :class:`FancyURLopener` subclasses :class:`URLopener` providing default handling
+ for the following HTTP response codes: 301, 302, 303, 307 and 401. For the 30x
+ response codes listed above, the :mailheader:`Location` header is used to fetch
+ the actual URL. For 401 response codes (authentication required), basic HTTP
+ authentication is performed. For the 30x response codes, recursion is bounded
+ by the value of the *maxtries* attribute, which defaults to 10.
+
+ For all other response codes, the method :meth:`http_error_default` is called
+ which you can override in subclasses to handle the error appropriately.
+
+ .. note::
+
+ According to the letter of :rfc:`2616`, 301 and 302 responses to POST requests
+ must not be automatically redirected without confirmation by the user. In
+ reality, browsers do allow automatic redirection of these responses, changing
+ the POST to a GET, and :mod:`urllib` reproduces this behaviour.
+
+ The parameters to the constructor are the same as those for :class:`URLopener`.
+
+ .. note::
+
+ When performing basic authentication, a :class:`FancyURLopener` instance calls
+ its :meth:`prompt_user_passwd` method. The default implementation asks the
+ users for the required information on the controlling terminal. A subclass may
+ override this method to support more appropriate behavior if needed.
+
+ The :class:`FancyURLopener` class offers one additional method that should be
+ overloaded to provide the appropriate behavior:
+
+ .. method:: prompt_user_passwd(host, realm)
+
+ Return information needed to authenticate the user at the given host in the
+ specified security realm. The return value should be a tuple, ``(user,
+ password)``, which can be used for basic authentication.
+
+ The implementation prompts for this information on the terminal; an application
+ should override this method to use an appropriate interaction model in the local
+ environment.
+
+.. class:: OpenerDirector()
+
+ The :class:`OpenerDirector` class opens URLs via :class:`BaseHandler`\ s chained
+ together. It manages the chaining of handlers, and recovery from errors.
+
+
+.. class:: BaseHandler()
+
+ This is the base class for all registered handlers --- and handles only the
+ simple mechanics of registration.
+
+
+.. class:: HTTPDefaultErrorHandler()
+
+ A class which defines a default handler for HTTP error responses; all responses
+ are turned into :exc:`HTTPError` exceptions.
+
+
+.. class:: HTTPRedirectHandler()
+
+ A class to handle redirections.
+
+
+.. class:: HTTPCookieProcessor([cookiejar])
+
+ A class to handle HTTP Cookies.
+
+
+.. class:: ProxyHandler([proxies])
+
+ Cause requests to go through a proxy. If *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 :envvar:`<protocol>_proxy`.
+ To disable autodetected proxy pass an empty dictionary.
+
+
+.. class:: HTTPPasswordMgr()
+
+ Keep a database of ``(realm, uri) -> (user, password)`` mappings.
+
+
+.. class:: HTTPPasswordMgrWithDefaultRealm()
+
+ Keep a database of ``(realm, uri) -> (user, password)`` mappings. A realm of
+ ``None`` is considered a catch-all realm, which is searched if no other realm
+ fits.
+
+
+.. class:: AbstractBasicAuthHandler([password_mgr])
+
+ This is a mixin class that helps with HTTP authentication, both to the remote
+ host and to a proxy. *password_mgr*, if given, should be something that is
+ compatible with :class:`HTTPPasswordMgr`; refer to section
+ :ref:`http-password-mgr` for information on the interface that must be
+ supported.
+
+
+.. class:: HTTPBasicAuthHandler([password_mgr])
+
+ Handle authentication with the remote host. *password_mgr*, if given, should be
+ something that is compatible with :class:`HTTPPasswordMgr`; refer to section
+ :ref:`http-password-mgr` for information on the interface that must be
+ supported.
+
+
+.. class:: ProxyBasicAuthHandler([password_mgr])
+
+ Handle authentication with the proxy. *password_mgr*, if given, should be
+ something that is compatible with :class:`HTTPPasswordMgr`; refer to section
+ :ref:`http-password-mgr` for information on the interface that must be
+ supported.
+
+
+.. class:: AbstractDigestAuthHandler([password_mgr])
+
+ This is a mixin class that helps with HTTP authentication, both to the remote
+ host and to a proxy. *password_mgr*, if given, should be something that is
+ compatible with :class:`HTTPPasswordMgr`; refer to section
+ :ref:`http-password-mgr` for information on the interface that must be
+ supported.
+
+
+.. class:: HTTPDigestAuthHandler([password_mgr])
+
+ Handle authentication with the remote host. *password_mgr*, if given, should be
+ something that is compatible with :class:`HTTPPasswordMgr`; refer to section
+ :ref:`http-password-mgr` for information on the interface that must be
+ supported.
+
+
+.. class:: ProxyDigestAuthHandler([password_mgr])
+
+ Handle authentication with the proxy. *password_mgr*, if given, should be
+ something that is compatible with :class:`HTTPPasswordMgr`; refer to section
+ :ref:`http-password-mgr` for information on the interface that must be
+ supported.
+
+
+.. class:: HTTPHandler()
+
+ A class to handle opening of HTTP URLs.
+
+
+.. class:: HTTPSHandler()
+
+ A class to handle opening of HTTPS URLs.
+
+
+.. class:: FileHandler()
+
+ Open local files.
+
+
+.. class:: FTPHandler()
+
+ Open FTP URLs.
+
+
+.. class:: CacheFTPHandler()
+
+ Open FTP URLs, keeping a cache of open FTP connections to minimize delays.
+
+
+.. class:: UnknownHandler()
+
+ A catch-all class to handle unknown URLs.
+
+
+.. _request-objects:
+
+Request Objects
+---------------
+
+The following methods describe all of :class:`Request`'s public interface, and
+so all must be overridden in subclasses.
+
+
+.. method:: Request.add_data(data)
+
+ Set the :class:`Request` data to *data*. This is ignored by all handlers except
+ HTTP handlers --- and there it should be a byte string, and will change the
+ request to be ``POST`` rather than ``GET``.
+
+
+.. method:: Request.get_method()
+
+ Return a string indicating the HTTP request method. This is only meaningful for
+ HTTP requests, and currently always returns ``'GET'`` or ``'POST'``.
+
+
+.. method:: Request.has_data()
+
+ Return whether the instance has a non-\ ``None`` data.
+
+
+.. method:: Request.get_data()
+
+ Return the instance's data.
+
+
+.. method:: 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 than one header with the same
+ name, and later calls will overwrite previous calls in case the *key* collides.
+ Currently, this is no loss of HTTP functionality, since all headers which have
+ meaning when used more than once have a (header-specific) way of gaining the
+ same functionality using only one header.
+
+
+.. method:: Request.add_unredirected_header(key, header)
+
+ Add a header that will not be added to a redirected request.
+
+
+.. method:: Request.has_header(header)
+
+ Return whether the instance has the named header (checks both regular and
+ unredirected).
+
+
+.. method:: Request.get_full_url()
+
+ Return the URL given in the constructor.
+
+
+.. method:: Request.get_type()
+
+ Return the type of the URL --- also known as the scheme.
+
+
+.. method:: Request.get_host()
+
+ Return the host to which a connection will be made.
+
+
+.. method:: Request.get_selector()
+
+ Return the selector --- the part of the URL that is sent to the server.
+
+
+.. method:: Request.set_proxy(host, type)
+
+ Prepare the request by connecting to a proxy server. The *host* and *type* will
+ replace those of the instance, and the instance's selector will be the original
+ URL given in the constructor.
+
+
+.. method:: Request.get_origin_req_host()
+
+ Return the request-host of the origin transaction, as defined by :rfc:`2965`.
+ See the documentation for the :class:`Request` constructor.
+
+
+.. method:: Request.is_unverifiable()
+
+ Return whether the request is unverifiable, as defined by RFC 2965. See the
+ documentation for the :class:`Request` constructor.
+
+
+.. _opener-director-objects:
+
+OpenerDirector Objects
+----------------------
+
+:class:`OpenerDirector` instances have the following methods:
+
+
+.. method:: OpenerDirector.add_handler(handler)
+
+ *handler* should be an instance of :class:`BaseHandler`. The following methods
+ are searched, and added to the possible chains (note that HTTP errors are a
+ special case).
+
+ * :meth:`protocol_open` --- signal that the handler knows how to open *protocol*
+ URLs.
+
+ * :meth:`http_error_type` --- signal that the handler knows how to handle HTTP
+ errors with HTTP error code *type*.
+
+ * :meth:`protocol_error` --- signal that the handler knows how to handle errors
+ from (non-\ ``http``) *protocol*.
+
+ * :meth:`protocol_request` --- signal that the handler knows how to pre-process
+ *protocol* requests.
+
+ * :meth:`protocol_response` --- signal that the handler knows how to
+ post-process *protocol* responses.
+
+
+.. method:: OpenerDirector.open(url[, data][, timeout])
+
+ Open the given *url* (which can be a request object or a string), optionally
+ passing the given *data*. Arguments, return values and exceptions raised are
+ the same as those of :func:`urlopen` (which simply calls the :meth:`open`
+ method on the currently installed global :class:`OpenerDirector`). The
+ optional *timeout* parameter specifies a timeout in seconds for blocking
+ operations like the connection attempt (if not specified, the global default
+ timeout setting will be usedi). The timeout feature actually works only for
+ HTTP, HTTPS, FTP and FTPS connections).
+
+
+.. method:: OpenerDirector.error(proto[, arg[, ...]])
+
+ Handle an error of the given protocol. This will call the registered error
+ handlers for the given protocol with the given arguments (which are protocol
+ specific). The HTTP protocol is a special case which uses the HTTP response
+ code to determine the specific error handler; refer to the :meth:`http_error_\*`
+ methods of the handler classes.
+
+ Return values and exceptions raised are the same as those of :func:`urlopen`.
+
+OpenerDirector objects open URLs in three stages:
+
+The order in which these methods are called within each stage is determined by
+sorting the handler instances.
+
+#. Every handler with a method named like :meth:`protocol_request` has that
+ method called to pre-process the request.
+
+#. Handlers with a method named like :meth:`protocol_open` are called to handle
+ the request. This stage ends when a handler either returns a non-\ :const:`None`
+ value (ie. a response), or raises an exception (usually :exc:`URLError`).
+ Exceptions are allowed to propagate.
+
+ In fact, the above algorithm is first tried for methods named
+ :meth:`default_open`. If all such methods return :const:`None`, the algorithm
+ is repeated for methods named like :meth:`protocol_open`. If all such methods
+ return :const:`None`, the algorithm is repeated for methods named
+ :meth:`unknown_open`.
+
+ Note that the implementation of these methods may involve calls of the parent
+ :class:`OpenerDirector` instance's :meth:`.open` and :meth:`.error` methods.
+
+#. Every handler with a method named like :meth:`protocol_response` has that
+ method called to post-process the response.
+
+
+.. _base-handler-objects:
+
+BaseHandler Objects
+-------------------
+
+:class:`BaseHandler` objects provide a couple of methods that are directly
+useful, and others that are meant to be used by derived classes. These are
+intended for direct use:
+
+
+.. method:: BaseHandler.add_parent(director)
+
+ Add a director as parent.
+
+
+.. method:: BaseHandler.close()
+
+ Remove any parents.
+
+The following members and methods should only be used by classes derived from
+:class:`BaseHandler`.
+
+.. note::
+
+ The convention has been adopted that subclasses defining
+ :meth:`protocol_request` or :meth:`protocol_response` methods are named
+ :class:`\*Processor`; all others are named :class:`\*Handler`.
+
+
+.. attribute:: BaseHandler.parent
+
+ A valid :class:`OpenerDirector`, which can be used to open using a different
+ protocol, or handle errors.
+
+
+.. method:: BaseHandler.default_open(req)
+
+ This method is *not* defined in :class:`BaseHandler`, but subclasses should
+ define it if they want to catch all URLs.
+
+ This method, if implemented, will be called by the parent
+ :class:`OpenerDirector`. It should return a file-like object as described in
+ the return value of the :meth:`open` of :class:`OpenerDirector`, or ``None``.
+ It should raise :exc:`URLError`, unless a truly exceptional thing happens (for
+ example, :exc:`MemoryError` should not be mapped to :exc:`URLError`).
+
+ This method will be called before any protocol-specific open method.
+
+
+.. method:: BaseHandler.protocol_open(req)
+ :noindex:
+
+ This method is *not* defined in :class:`BaseHandler`, but subclasses should
+ define it if they want to handle URLs with the given protocol.
+
+ This method, if defined, will be called by the parent :class:`OpenerDirector`.
+ Return values should be the same as for :meth:`default_open`.
+
+
+.. method:: BaseHandler.unknown_open(req)
+
+ This method is *not* defined in :class:`BaseHandler`, but subclasses should
+ define it if they want to catch all URLs with no specific registered handler to
+ open it.
+
+ This method, if implemented, will be called by the :attr:`parent`
+ :class:`OpenerDirector`. Return values should be the same as for
+ :meth:`default_open`.
+
+
+.. method:: BaseHandler.http_error_default(req, fp, code, msg, hdrs)
+
+ This method is *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.
+
+ *req* will be a :class:`Request` object, *fp* will be a file-like object with
+ the HTTP error body, *code* will be the three-digit code of the error, *msg*
+ will be the user-visible explanation of the code and *hdrs* will be a mapping
+ object with the headers of the error.
+
+ Return values and exceptions raised should be the same as those of
+ :func:`urlopen`.
+
+
+.. method:: BaseHandler.http_error_nnn(req, fp, code, msg, hdrs)
+
+ *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 *nnn* occurs.
+
+ Subclasses should override this method to handle specific HTTP errors.
+
+ Arguments, return values and exceptions raised should be the same as for
+ :meth:`http_error_default`.
+
+
+.. method:: BaseHandler.protocol_request(req)
+ :noindex:
+
+ This method is *not* defined in :class:`BaseHandler`, but subclasses should
+ define it if they want to pre-process requests of the given protocol.
+
+ This method, if defined, will be called by the parent :class:`OpenerDirector`.
+ *req* will be a :class:`Request` object. The return value should be a
+ :class:`Request` object.
+
+
+.. method:: BaseHandler.protocol_response(req, response)
+ :noindex:
+
+ This method is *not* defined in :class:`BaseHandler`, but subclasses should
+ define it if they want to post-process responses of the given protocol.
+
+ This method, if defined, will be called by the parent :class:`OpenerDirector`.
+ *req* will be a :class:`Request` object. *response* will be an object
+ implementing the same interface as the return value of :func:`urlopen`. The
+ return value should implement the same interface as the return value of
+ :func:`urlopen`.
+
+
+.. _http-redirect-handler:
+
+HTTPRedirectHandler Objects
+---------------------------
+
+.. note::
+
+ Some HTTP redirections require action from this module's client code. If this
+ is the case, :exc:`HTTPError` is raised. See :rfc:`2616` for details of the
+ precise meanings of the various redirection codes.
+
+
+.. method:: HTTPRedirectHandler.redirect_request(req, fp, code, msg, hdrs)
+
+ Return a :class:`Request` or ``None`` in response to a redirect. This is called
+ by the default implementations of the :meth:`http_error_30\*` methods when a
+ redirection is received from the server. If a redirection should take place,
+ return a new :class:`Request` to allow :meth:`http_error_30\*` to perform the
+ redirect. Otherwise, raise :exc:`HTTPError` if no other handler should try to
+ handle this URL, or return ``None`` if you can't but another handler might.
+
+ .. note::
+
+ The default implementation of this method does not strictly follow :rfc:`2616`,
+ which says that 301 and 302 responses to ``POST`` requests must not be
+ automatically redirected without confirmation by the user. In reality, browsers
+ do allow automatic redirection of these responses, changing the POST to a
+ ``GET``, and the default implementation reproduces this behavior.
+
+
+.. method:: HTTPRedirectHandler.http_error_301(req, fp, code, msg, hdrs)
+
+ Redirect to the ``Location:`` URL. This method is called by the parent
+ :class:`OpenerDirector` when getting an HTTP 'moved permanently' response.
+
+
+.. method:: HTTPRedirectHandler.http_error_302(req, fp, code, msg, hdrs)
+
+ The same as :meth:`http_error_301`, but called for the 'found' response.
+
+
+.. method:: HTTPRedirectHandler.http_error_303(req, fp, code, msg, hdrs)
+
+ The same as :meth:`http_error_301`, but called for the 'see other' response.
+
+
+.. method:: HTTPRedirectHandler.http_error_307(req, fp, code, msg, hdrs)
+
+ The same as :meth:`http_error_301`, but called for the 'temporary redirect'
+ response.
+
+
+.. _http-cookie-processor:
+
+HTTPCookieProcessor Objects
+---------------------------
+
+:class:`HTTPCookieProcessor` instances have one attribute:
+
+.. attribute:: HTTPCookieProcessor.cookiejar
+
+ The :class:`http.cookiejar.CookieJar` in which cookies are stored.
+
+
+.. _proxy-handler:
+
+ProxyHandler Objects
+--------------------
+
+
+.. method:: ProxyHandler.protocol_open(request)
+ :noindex:
+
+ The :class:`ProxyHandler` will have a method :meth:`protocol_open` for every
+ *protocol* which has a proxy in the *proxies* dictionary given in the
+ constructor. The method will modify requests to go through the proxy, by
+ calling ``request.set_proxy()``, and call the next handler in the chain to
+ actually execute the protocol.
+
+
+.. _http-password-mgr:
+
+HTTPPasswordMgr Objects
+-----------------------
+
+These methods are available on :class:`HTTPPasswordMgr` and
+:class:`HTTPPasswordMgrWithDefaultRealm` objects.
+
+
+.. method:: HTTPPasswordMgr.add_password(realm, uri, user, passwd)
+
+ *uri* can be either a single URI, or a sequence of URIs. *realm*, *user* and
+ *passwd* must be strings. This causes ``(user, passwd)`` to be used as
+ authentication tokens when authentication for *realm* and a super-URI of any of
+ the given URIs is given.
+
+
+.. method:: HTTPPasswordMgr.find_user_password(realm, authuri)
+
+ Get user/password for given realm and URI, if any. This method will return
+ ``(None, None)`` if there is no matching user/password.
+
+ For :class:`HTTPPasswordMgrWithDefaultRealm` objects, the realm ``None`` will be
+ searched if the given *realm* has no matching user/password.
+
+
+.. _abstract-basic-auth-handler:
+
+AbstractBasicAuthHandler Objects
+--------------------------------
+
+
+.. method:: AbstractBasicAuthHandler.http_error_auth_reqed(authreq, host, req, headers)
+
+ Handle an authentication request by getting a user/password pair, and re-trying
+ the request. *authreq* should be the name of the header where the information
+ about the realm is included in the request, *host* specifies the URL and path to
+ authenticate for, *req* should be the (failed) :class:`Request` object, and
+ *headers* should be the error headers.
+
+ *host* is either an authority (e.g. ``"python.org"``) or a URL containing an
+ authority component (e.g. ``"http://python.org/"``). In either case, the
+ authority must not contain a userinfo component (so, ``"python.org"`` and
+ ``"python.org:80"`` are fine, ``"joe:password@python.org"`` is not).
+
+
+.. _http-basic-auth-handler:
+
+HTTPBasicAuthHandler Objects
+----------------------------
+
+
+.. method:: HTTPBasicAuthHandler.http_error_401(req, fp, code, msg, hdrs)
+
+ Retry the request with authentication information, if available.
+
+
+.. _proxy-basic-auth-handler:
+
+ProxyBasicAuthHandler Objects
+-----------------------------
+
+
+.. method:: ProxyBasicAuthHandler.http_error_407(req, fp, code, msg, hdrs)
+
+ Retry the request with authentication information, if available.
+
+
+.. _abstract-digest-auth-handler:
+
+AbstractDigestAuthHandler Objects
+---------------------------------
+
+
+.. method:: AbstractDigestAuthHandler.http_error_auth_reqed(authreq, host, req, headers)
+
+ *authreq* should be the name of the header where the information about the realm
+ is included in the request, *host* should be the host to authenticate to, *req*
+ should be the (failed) :class:`Request` object, and *headers* should be the
+ error headers.
+
+
+.. _http-digest-auth-handler:
+
+HTTPDigestAuthHandler Objects
+-----------------------------
+
+
+.. method:: HTTPDigestAuthHandler.http_error_401(req, fp, code, msg, hdrs)
+
+ Retry the request with authentication information, if available.
+
+
+.. _proxy-digest-auth-handler:
+
+ProxyDigestAuthHandler Objects
+------------------------------
+
+
+.. method:: ProxyDigestAuthHandler.http_error_407(req, fp, code, msg, hdrs)
+
+ Retry the request with authentication information, if available.
+
+
+.. _http-handler-objects:
+
+HTTPHandler Objects
+-------------------
+
+
+.. method:: HTTPHandler.http_open(req)
+
+ Send an HTTP request, which can be either GET or POST, depending on
+ ``req.has_data()``.
+
+
+.. _https-handler-objects:
+
+HTTPSHandler Objects
+--------------------
+
+
+.. method:: HTTPSHandler.https_open(req)
+
+ Send an HTTPS request, which can be either GET or POST, depending on
+ ``req.has_data()``.
+
+
+.. _file-handler-objects:
+
+FileHandler Objects
+-------------------
+
+
+.. method:: FileHandler.file_open(req)
+
+ Open the file locally, if there is no host name, or the host name is
+ ``'localhost'``. Change the protocol to ``ftp`` otherwise, and retry opening it
+ using :attr:`parent`.
+
+
+.. _ftp-handler-objects:
+
+FTPHandler Objects
+------------------
+
+
+.. method:: FTPHandler.ftp_open(req)
+
+ Open the FTP file indicated by *req*. The login is always done with empty
+ username and password.
+
+
+.. _cacheftp-handler-objects:
+
+CacheFTPHandler Objects
+-----------------------
+
+:class:`CacheFTPHandler` objects are :class:`FTPHandler` objects with the
+following additional methods:
+
+
+.. method:: CacheFTPHandler.setTimeout(t)
+
+ Set timeout of connections to *t* seconds.
+
+
+.. method:: CacheFTPHandler.setMaxConns(m)
+
+ Set maximum number of cached connections to *m*.
+
+
+.. _unknown-handler-objects:
+
+UnknownHandler Objects
+----------------------
+
+
+.. method:: UnknownHandler.unknown_open()
+
+ Raise a :exc:`URLError` exception.
+
+
+.. _http-error-processor-objects:
+
+HTTPErrorProcessor Objects
+--------------------------
+
+.. method:: HTTPErrorProcessor.unknown_open()
+
+ Process HTTP error responses.
+
+ For 200 error codes, the response object is returned immediately.
+
+ For non-200 error codes, this simply passes the job on to the
+ :meth:`protocol_error_code` handler methods, via :meth:`OpenerDirector.error`.
+ Eventually, :class:`urllib2.HTTPDefaultErrorHandler` will raise an
+ :exc:`HTTPError` if no other handler handles the error.
+
+.. _urllib2-examples:
+
+Examples
+--------
+
+This example gets the python.org main page and displays the first 100 bytes of
+it::
+
+ >>> import urllib.request
+ >>> f = urllib.request.urlopen('http://www.python.org/')
+ >>> print(f.read(100))
+ <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+ <?xml-stylesheet href="./css/ht2html
+
+Here we are sending a data-stream to the stdin of a CGI and reading the data it
+returns to us. Note that this example will only work when the Python
+installation supports SSL. ::
+
+ >>> import urllib.request
+ >>> req = urllib.request.Request(url='https://localhost/cgi-bin/test.cgi',
+ ... data='This data is passed to stdin of the CGI')
+ >>> f = urllib.request.urlopen(req)
+ >>> print(f.read())
+ Got Data: "This data is passed to stdin of the CGI"
+
+The code for the sample CGI used in the above example is::
+
+ #!/usr/bin/env python
+ import sys
+ data = sys.stdin.read()
+ print('Content-type: text-plain\n\nGot Data: "%s"' % data)
+
+Use of Basic HTTP Authentication::
+
+ import urllib.request
+ # Create an OpenerDirector with support for Basic HTTP Authentication...
+ auth_handler = urllib.request.HTTPBasicAuthHandler()
+ auth_handler.add_password(realm='PDQ Application',
+ uri='https://mahler:8092/site-updates.py',
+ user='klem',
+ passwd='kadidd!ehopper')
+ opener = urllib.request.build_opener(auth_handler)
+ # ...and install it globally so it can be used with urlopen.
+ urllib.request.install_opener(opener)
+ urllib.request.urlopen('http://www.example.com/login.html')
+
+:func:`build_opener` provides many handlers by default, including a
+:class:`ProxyHandler`. By default, :class:`ProxyHandler` uses the environment
+variables named ``<scheme>_proxy``, where ``<scheme>`` is the URL scheme
+involved. For example, the :envvar:`http_proxy` environment variable is read to
+obtain the HTTP proxy's URL.
+
+This example replaces the default :class:`ProxyHandler` with one that uses
+programatically-supplied proxy URLs, and adds proxy authorization support with
+:class:`ProxyBasicAuthHandler`. ::
+
+ proxy_handler = urllib.request.ProxyHandler({'http': 'http://www.example.com:3128/'})
+ proxy_auth_handler = urllib.request.HTTPBasicAuthHandler()
+ proxy_auth_handler.add_password('realm', 'host', 'username', 'password')
+
+ opener = build_opener(proxy_handler, proxy_auth_handler)
+ # This time, rather than install the OpenerDirector, we use it directly:
+ opener.open('http://www.example.com/login.html')
+
+Adding HTTP headers:
+
+Use the *headers* argument to the :class:`Request` constructor, or::
+
+ import urllib
+ req = urllib.request.Request('http://www.example.com/')
+ req.add_header('Referer', 'http://www.python.org/')
+ r = urllib.request.urlopen(req)
+
+:class:`OpenerDirector` automatically adds a :mailheader:`User-Agent` header to
+every :class:`Request`. To change this::
+
+ import urllib
+ opener = urllib.request.build_opener()
+ opener.addheaders = [('User-agent', 'Mozilla/5.0')]
+ opener.open('http://www.example.com/')
+
+Also, remember that a few standard headers (:mailheader:`Content-Length`,
+:mailheader:`Content-Type` and :mailheader:`Host`) are added when the
+:class:`Request` is passed to :func:`urlopen` (or :meth:`OpenerDirector.open`).
+
+.. _urllib-examples:
+
+Here is an example session that uses the ``GET`` method to retrieve a URL
+containing parameters::
+
+ >>> import urllib.request
+ >>> import urllib.parse
+ >>> params = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
+ >>> f = urllib.request.urlopen("http://www.musi-cal.com/cgi-bin/query?%s" % params)
+ >>> print(f.read())
+
+The following example uses the ``POST`` method instead::
+
+ >>> import urllib.request
+ >>> import urllib.parse
+ >>> params = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
+ >>> f = urllib.request.urlopen("http://www.musi-cal.com/cgi-bin/query", params)
+ >>> print(f.read())
+
+The following example uses an explicitly specified HTTP proxy, overriding
+environment settings::
+
+ >>> import urllib.request
+ >>> proxies = {'http': 'http://proxy.example.com:8080/'}
+ >>> opener = urllib.request.FancyURLopener(proxies)
+ >>> f = opener.open("http://www.python.org")
+ >>> f.read()
+
+The following example uses no proxies at all, overriding environment settings::
+
+ >>> import urllib.request
+ >>> opener = urllib.request.FancyURLopener({})
+ >>> f = opener.open("http://www.python.org/")
+ >>> f.read()
+
+
+:mod:`urllib.request` Restrictions
+----------------------------------
+
+ .. index::
+ pair: HTTP; protocol
+ pair: FTP; protocol
+
+* Currently, only the following protocols are supported: HTTP, (versions 0.9 and
+ 1.0), FTP, and local files.
+
+* The caching feature of :func:`urlretrieve` has been disabled until I find the
+ time to hack proper processing of Expiration time headers.
+
+* There should be a function to query whether a particular URL is in the cache.
+
+* For backward compatibility, if a URL appears to point to a local file but the
+ file can't be opened, the URL is re-interpreted using the FTP protocol. This
+ can sometimes cause confusing error messages.
+
+* The :func:`urlopen` and :func:`urlretrieve` functions can cause arbitrarily
+ long delays while waiting for a network connection to be set up. This means
+ that it is difficult to build an interactive Web client using these functions
+ without using threads.
+
+ .. index::
+ single: HTML
+ pair: HTTP; protocol
+
+* The data returned by :func:`urlopen` or :func:`urlretrieve` is the raw data
+ returned by the server. This may be binary data (such as an image), plain text
+ or (for example) HTML. The HTTP protocol provides type information in the reply
+ header, which can be inspected by looking at the :mailheader:`Content-Type`
+ header. If the returned data is HTML, you can use the module
+ :mod:`html.parser` to parse it.
+
+ .. index:: single: FTP
+
+* The code handling the FTP protocol cannot differentiate between a file and a
+ directory. This can lead to unexpected behavior when attempting to read a URL
+ that points to a file that is not accessible. If the URL ends in a ``/``, it is
+ assumed to refer to a directory and will be handled accordingly. But if an
+ attempt to read a file leads to a 550 error (meaning the URL cannot be found or
+ is not accessible, often for permission reasons), then the path is treated as a
+ directory in order to handle the case when a directory is specified by a URL but
+ the trailing ``/`` has been left off. This can cause misleading results when
+ you try to fetch a file whose read permissions make it inaccessible; the FTP
+ code will try to read it, fail with a 550 error, and then perform a directory
+ listing for the unreadable file. If fine-grained control is needed, consider
+ using the :mod:`ftplib` module, subclassing :class:`FancyURLOpener`, or changing
+ *_urlopener* to meet your needs.
+
+:mod:`urllib.response` --- Response classes used by urllib.
+===========================================================
+.. module:: urllib.response
+ :synopsis: Response classes used by urllib.
+
+The :mod:`urllib.response` module defines functions and classes which define a
+minimal file like interface, including read() and readline(). The typical
+response object is an addinfourl instance, which defines and info() method and
+that returns headers and a geturl() method that returns the url.
+Functions defined by this module are used internally by the
+:mod:`urllib.request` module.
+