1280 lines
46 KiB
ReStructuredText
1280 lines
46 KiB
ReStructuredText
:mod:`urllib.request` --- extensible library for opening URLs
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=============================================================
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.. module:: urllib.request
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:synopsis: Next generation URL opening library.
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.. moduleauthor:: Jeremy Hylton <jeremy@alum.mit.edu>
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.. sectionauthor:: Moshe Zadka <moshez@users.sourceforge.net>
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The :mod:`urllib.request` module defines functions and classes which help in
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opening URLs (mostly HTTP) in a complex world --- basic and digest
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authentication, redirections, cookies and more.
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The :mod:`urllib.request` module defines the following functions:
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.. function:: urlopen(url, data=None[, timeout])
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Open the URL *url*, which can be either a string or a
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:class:`Request` object.
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*data* may be a string specifying additional data to send to the
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server, or ``None`` if no such data is needed. Currently HTTP
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requests are the only ones that use *data*; the HTTP request will
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be a POST instead of a GET when the *data* parameter is provided.
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*data* should be a buffer in the standard
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:mimetype:`application/x-www-form-urlencoded` format. The
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:func:`urllib.parse.urlencode` function takes a mapping or sequence
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of 2-tuples and returns a string in this format.
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The optional *timeout* parameter specifies a timeout in seconds for
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blocking operations like the connection attempt (if not specified,
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the global default timeout setting will be used). This actually
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only works for HTTP, HTTPS, FTP and FTPS connections.
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This function returns a file-like object with two additional methods from
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the :mod:`urllib.response` module
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* :meth:`geturl` --- return the URL of the resource retrieved,
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commonly used to determine if a redirect was followed
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* :meth:`info` --- return the meta-information of the page, such as headers,
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in the form of an :class:`http.client.HTTPMessage` instance (see `Quick
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Reference to HTTP Headers <http://www.cs.tut.fi/~jkorpela/http.html>`_)
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Raises :exc:`URLError` on errors.
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Note that ``None`` may be returned if no handler handles the request (though
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the default installed global :class:`OpenerDirector` uses
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:class:`UnknownHandler` to ensure this never happens).
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In addition, default installed :class:`ProxyHandler` makes sure the requests
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are handled through the proxy when they are set.
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The legacy ``urllib.urlopen`` function from Python 2.6 and earlier has been
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discontinued; :func:`urlopen` corresponds to the old ``urllib2.urlopen``.
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Proxy handling, which was done by passing a dictionary parameter to
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``urllib.urlopen``, can be obtained by using :class:`ProxyHandler` objects.
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.. function:: install_opener(opener)
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Install an :class:`OpenerDirector` instance as the default global opener.
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Installing an opener is only necessary if you want urlopen to use that opener;
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otherwise, simply call :meth:`OpenerDirector.open` instead of :func:`urlopen`.
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The code does not check for a real :class:`OpenerDirector`, and any class with
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the appropriate interface will work.
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.. function:: build_opener([handler, ...])
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Return an :class:`OpenerDirector` instance, which chains the handlers in the
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order given. *handler*\s can be either instances of :class:`BaseHandler`, or
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subclasses of :class:`BaseHandler` (in which case it must be possible to call
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the constructor without any parameters). Instances of the following classes
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will be in front of the *handler*\s, unless the *handler*\s contain them,
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instances of them or subclasses of them: :class:`ProxyHandler`,
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:class:`UnknownHandler`, :class:`HTTPHandler`, :class:`HTTPDefaultErrorHandler`,
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:class:`HTTPRedirectHandler`, :class:`FTPHandler`, :class:`FileHandler`,
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:class:`HTTPErrorProcessor`.
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If the Python installation has SSL support (i.e., if the :mod:`ssl` module
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can be imported), :class:`HTTPSHandler` will also be added.
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A :class:`BaseHandler` subclass may also change its :attr:`handler_order`
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member variable to modify its position in the handlers list.
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.. function:: urlretrieve(url, filename=None, reporthook=None, data=None)
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Copy a network object denoted by a URL to a local file, if necessary. If the URL
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points to a local file, or a valid cached copy of the object exists, the object
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is not copied. Return a tuple ``(filename, headers)`` where *filename* is the
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local file name under which the object can be found, and *headers* is whatever
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the :meth:`info` method of the object returned by :func:`urlopen` returned (for
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a remote object, possibly cached). Exceptions are the same as for
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:func:`urlopen`.
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The second argument, if present, specifies the file location to copy to (if
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absent, the location will be a tempfile with a generated name). The third
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argument, if present, is a hook function that will be called once on
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establishment of the network connection and once after each block read
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thereafter. The hook will be passed three arguments; a count of blocks
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transferred so far, a block size in bytes, and the total size of the file. The
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third argument may be ``-1`` on older FTP servers which do not return a file
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size in response to a retrieval request.
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If the *url* uses the :file:`http:` scheme identifier, the optional *data*
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argument may be given to specify a ``POST`` request (normally the request type
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is ``GET``). The *data* argument must in standard
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:mimetype:`application/x-www-form-urlencoded` format; see the :func:`urlencode`
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function below.
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:func:`urlretrieve` will raise :exc:`ContentTooShortError` when it detects that
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the amount of data available was less than the expected amount (which is the
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size reported by a *Content-Length* header). This can occur, for example, when
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the download is interrupted.
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The *Content-Length* is treated as a lower bound: if there's more data to read,
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urlretrieve reads more data, but if less data is available, it raises the
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exception.
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You can still retrieve the downloaded data in this case, it is stored in the
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:attr:`content` attribute of the exception instance.
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If no *Content-Length* header was supplied, urlretrieve can not check the size
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of the data it has downloaded, and just returns it. In this case you just have
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to assume that the download was successful.
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.. data:: _urlopener
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The public functions :func:`urlopen` and :func:`urlretrieve` create an instance
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of the :class:`FancyURLopener` class and use it to perform their requested
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actions. To override this functionality, programmers can create a subclass of
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:class:`URLopener` or :class:`FancyURLopener`, then assign an instance of that
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class to the ``urllib._urlopener`` variable before calling the desired function.
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For example, applications may want to specify a different
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:mailheader:`User-Agent` header than :class:`URLopener` defines. This can be
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accomplished with the following code::
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import urllib.request
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class AppURLopener(urllib.request.FancyURLopener):
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version = "App/1.7"
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urllib._urlopener = AppURLopener()
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.. function:: urlcleanup()
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Clear the cache that may have been built up by previous calls to
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:func:`urlretrieve`.
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.. function:: pathname2url(path)
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Convert the pathname *path* from the local syntax for a path to the form used in
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the path component of a URL. This does not produce a complete URL. The return
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value will already be quoted using the :func:`quote` function.
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.. function:: url2pathname(path)
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Convert the path component *path* from an encoded URL to the local syntax for a
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path. This does not accept a complete URL. This function uses :func:`unquote`
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to decode *path*.
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.. function:: getproxies()
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This helper function returns a dictionary of scheme to proxy server URL
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mappings. It scans the environment for variables named ``<scheme>_proxy``
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for all operating systems first, and when it cannot find it, looks for proxy
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information from Mac OSX System Configuration for Mac OS X and Windows
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Systems Registry for Windows.
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The following classes are provided:
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.. class:: Request(url, data=None, headers={}, origin_req_host=None, unverifiable=False)
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This class is an abstraction of a URL request.
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*url* should be a string containing a valid URL.
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*data* may be a string specifying additional data to send to the
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server, or ``None`` if no such data is needed. Currently HTTP
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requests are the only ones that use *data*; the HTTP request will
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be a POST instead of a GET when the *data* parameter is provided.
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*data* should be a buffer in the standard
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:mimetype:`application/x-www-form-urlencoded` format. The
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:func:`urllib.parse.urlencode` function takes a mapping or sequence
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of 2-tuples and returns a string in this format.
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*headers* should be a dictionary, and will be treated as if
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:meth:`add_header` was called with each key and value as arguments.
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This is often used to "spoof" the ``User-Agent`` header, which is
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used by a browser to identify itself -- some HTTP servers only
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allow requests coming from common browsers as opposed to scripts.
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For example, Mozilla Firefox may identify itself as ``"Mozilla/5.0
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(X11; U; Linux i686) Gecko/20071127 Firefox/2.0.0.11"``, while
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:mod:`urllib`'s default user agent string is
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``"Python-urllib/2.6"`` (on Python 2.6).
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The final two arguments are only of interest for correct handling
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of third-party HTTP cookies:
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*origin_req_host* should be the request-host of the origin
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transaction, as defined by :rfc:`2965`. It defaults to
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``http.cookiejar.request_host(self)``. This is the host name or IP
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address of the original request that was initiated by the user.
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For example, if the request is for an image in an HTML document,
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this should be the request-host of the request for the page
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containing the image.
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*unverifiable* should indicate whether the request is unverifiable,
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as defined by RFC 2965. It defaults to False. An unverifiable
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request is one whose URL the user did not have the option to
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approve. For example, if the request is for an image in an HTML
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document, and the user had no option to approve the automatic
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fetching of the image, this should be true.
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.. class:: URLopener(proxies=None, **x509)
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Base class for opening and reading URLs. Unless you need to support opening
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objects using schemes other than :file:`http:`, :file:`ftp:`, or :file:`file:`,
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you probably want to use :class:`FancyURLopener`.
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By default, the :class:`URLopener` class sends a :mailheader:`User-Agent` header
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of ``urllib/VVV``, where *VVV* is the :mod:`urllib` version number.
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Applications can define their own :mailheader:`User-Agent` header by subclassing
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:class:`URLopener` or :class:`FancyURLopener` and setting the class attribute
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:attr:`version` to an appropriate string value in the subclass definition.
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The optional *proxies* parameter should be a dictionary mapping scheme names to
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proxy URLs, where an empty dictionary turns proxies off completely. Its default
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value is ``None``, in which case environmental proxy settings will be used if
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present, as discussed in the definition of :func:`urlopen`, above.
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Additional keyword parameters, collected in *x509*, may be used for
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authentication of the client when using the :file:`https:` scheme. The keywords
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*key_file* and *cert_file* are supported to provide an SSL key and certificate;
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both are needed to support client authentication.
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:class:`URLopener` objects will raise an :exc:`IOError` exception if the server
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returns an error code.
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.. method:: open(fullurl, data=None)
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Open *fullurl* using the appropriate protocol. This method sets up cache and
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proxy information, then calls the appropriate open method with its input
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arguments. If the scheme is not recognized, :meth:`open_unknown` is called.
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The *data* argument has the same meaning as the *data* argument of
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:func:`urlopen`.
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.. method:: open_unknown(fullurl, data=None)
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Overridable interface to open unknown URL types.
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.. method:: retrieve(url, filename=None, reporthook=None, data=None)
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Retrieves the contents of *url* and places it in *filename*. The return value
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is a tuple consisting of a local filename and either a
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:class:`email.message.Message` object containing the response headers (for remote
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URLs) or ``None`` (for local URLs). The caller must then open and read the
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contents of *filename*. If *filename* is not given and the URL refers to a
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local file, the input filename is returned. If the URL is non-local and
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*filename* is not given, the filename is the output of :func:`tempfile.mktemp`
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with a suffix that matches the suffix of the last path component of the input
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URL. If *reporthook* is given, it must be a function accepting three numeric
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parameters. It will be called after each chunk of data is read from the
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network. *reporthook* is ignored for local URLs.
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If the *url* uses the :file:`http:` scheme identifier, the optional *data*
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argument may be given to specify a ``POST`` request (normally the request type
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is ``GET``). The *data* argument must in standard
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:mimetype:`application/x-www-form-urlencoded` format; see the :func:`urlencode`
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function below.
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.. attribute:: version
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Variable that specifies the user agent of the opener object. To get
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:mod:`urllib` to tell servers that it is a particular user agent, set this in a
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subclass as a class variable or in the constructor before calling the base
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constructor.
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.. class:: FancyURLopener(...)
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:class:`FancyURLopener` subclasses :class:`URLopener` providing default handling
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for the following HTTP response codes: 301, 302, 303, 307 and 401. For the 30x
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response codes listed above, the :mailheader:`Location` header is used to fetch
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the actual URL. For 401 response codes (authentication required), basic HTTP
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authentication is performed. For the 30x response codes, recursion is bounded
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by the value of the *maxtries* attribute, which defaults to 10.
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For all other response codes, the method :meth:`http_error_default` is called
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which you can override in subclasses to handle the error appropriately.
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.. note::
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According to the letter of :rfc:`2616`, 301 and 302 responses to POST requests
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must not be automatically redirected without confirmation by the user. In
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reality, browsers do allow automatic redirection of these responses, changing
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the POST to a GET, and :mod:`urllib` reproduces this behaviour.
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The parameters to the constructor are the same as those for :class:`URLopener`.
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.. note::
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When performing basic authentication, a :class:`FancyURLopener` instance calls
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its :meth:`prompt_user_passwd` method. The default implementation asks the
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users for the required information on the controlling terminal. A subclass may
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override this method to support more appropriate behavior if needed.
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The :class:`FancyURLopener` class offers one additional method that should be
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overloaded to provide the appropriate behavior:
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.. method:: prompt_user_passwd(host, realm)
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Return information needed to authenticate the user at the given host in the
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specified security realm. The return value should be a tuple, ``(user,
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password)``, which can be used for basic authentication.
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The implementation prompts for this information on the terminal; an application
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should override this method to use an appropriate interaction model in the local
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environment.
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.. class:: 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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.. class:: BaseHandler()
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This is the base class for all registered handlers --- and handles only the
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simple mechanics of registration.
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.. class:: HTTPDefaultErrorHandler()
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A class which defines a default handler for HTTP error responses; all responses
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are turned into :exc:`HTTPError` exceptions.
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.. class:: HTTPRedirectHandler()
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A class to handle redirections.
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.. class:: HTTPCookieProcessor(cookiejar=None)
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A class to handle HTTP Cookies.
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.. class:: ProxyHandler(proxies=None)
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Cause requests to go through a proxy. If *proxies* is given, it must be a
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dictionary mapping protocol names to URLs of proxies. The default is to read the
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list of proxies from the environment variables :envvar:`<protocol>_proxy`.
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If no proxy environment variables are set, in a Windows environment, proxy
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settings are obtained from the registry's Internet Settings section and in a
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Mac OS X environment, proxy information is retrieved from the OS X System
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Configuration Framework.
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To disable autodetected proxy pass an empty dictionary.
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.. class:: HTTPPasswordMgr()
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Keep a database of ``(realm, uri) -> (user, password)`` mappings.
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.. class:: HTTPPasswordMgrWithDefaultRealm()
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Keep a database of ``(realm, uri) -> (user, password)`` mappings. A realm of
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``None`` is considered a catch-all realm, which is searched if no other realm
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fits.
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.. class:: AbstractBasicAuthHandler(password_mgr=None)
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This is a mixin class that helps with HTTP authentication, both to the remote
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host and to a proxy. *password_mgr*, if given, should be something that is
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compatible with :class:`HTTPPasswordMgr`; refer to section
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:ref:`http-password-mgr` for information on the interface that must be
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supported.
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.. class:: HTTPBasicAuthHandler(password_mgr=None)
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Handle authentication with the remote host. *password_mgr*, if given, should be
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something that is compatible with :class:`HTTPPasswordMgr`; refer to section
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:ref:`http-password-mgr` for information on the interface that must be
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supported.
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.. class:: ProxyBasicAuthHandler(password_mgr=None)
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Handle authentication with the proxy. *password_mgr*, if given, should be
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something that is compatible with :class:`HTTPPasswordMgr`; refer to section
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:ref:`http-password-mgr` for information on the interface that must be
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supported.
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.. class:: AbstractDigestAuthHandler(password_mgr=None)
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This is a mixin class that helps with HTTP authentication, both to the remote
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host and to a proxy. *password_mgr*, if given, should be something that is
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compatible with :class:`HTTPPasswordMgr`; refer to section
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:ref:`http-password-mgr` for information on the interface that must be
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supported.
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.. class:: HTTPDigestAuthHandler(password_mgr=None)
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Handle authentication with the remote host. *password_mgr*, if given, should be
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something that is compatible with :class:`HTTPPasswordMgr`; refer to section
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:ref:`http-password-mgr` for information on the interface that must be
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supported.
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.. class:: ProxyDigestAuthHandler(password_mgr=None)
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Handle authentication with the proxy. *password_mgr*, if given, should be
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something that is compatible with :class:`HTTPPasswordMgr`; refer to section
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:ref:`http-password-mgr` for information on the interface that must be
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supported.
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.. class:: HTTPHandler()
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A class to handle opening of HTTP URLs.
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.. class:: HTTPSHandler()
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A class to handle opening of HTTPS URLs.
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.. class:: FileHandler()
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Open local files.
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.. class:: FTPHandler()
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Open FTP URLs.
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.. class:: CacheFTPHandler()
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Open FTP URLs, keeping a cache of open FTP connections to minimize delays.
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.. class:: UnknownHandler()
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A catch-all class to handle unknown URLs.
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.. _request-objects:
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Request Objects
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---------------
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The following methods describe :class:`Request`'s public interface,
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and so all may be overridden in subclasses. It also defines several
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public attributes that can be used by clients to inspect the parsed
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request.
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.. attribute:: Request.full_url
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The original URL passed to the constructor.
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.. attribute:: Request.type
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The URI scheme.
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.. attribute:: Request.host
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The URI authority, typically a host, but may also contain a port
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separated by a colon.
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.. attribute:: Request.origin_req_host
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|
The original host for the request, without port.
|
|
|
|
.. attribute:: Request.selector
|
|
|
|
The URI path. If the :class:`Request` uses a proxy, then selector
|
|
will be the full url that is passed to the proxy.
|
|
|
|
.. attribute:: Request.data
|
|
|
|
The entity body for the request, or None if not specified.
|
|
|
|
.. attribute:: Request.unverifiable
|
|
|
|
boolean, indicates whether the request is unverifiable as defined
|
|
by RFC 2965.
|
|
|
|
.. 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=None[, 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, *args)
|
|
|
|
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, newurl)
|
|
|
|
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 to *newurl*. 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:`` or ``URI:`` 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
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--------------------------
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.. method:: HTTPErrorProcessor.unknown_open()
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Process HTTP error responses.
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For 200 error codes, the response object is returned immediately.
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For non-200 error codes, this simply passes the job on to the
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:meth:`protocol_error_code` handler methods, via :meth:`OpenerDirector.error`.
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Eventually, :class:`HTTPDefaultErrorHandler` will raise an
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:exc:`HTTPError` if no other handler handles the error.
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.. _urllib-request-examples:
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Examples
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--------
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This example gets the python.org main page and displays the first 300 bytes of
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it.::
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>>> import urllib.request
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>>> f = urllib.request.urlopen('http://www.python.org/')
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>>> print(f.read(300))
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b'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">\n\n\n<html
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xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">\n\n<head>\n
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />\n
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<title>Python Programming '
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Note that urlopen returns a bytes object. This is because there is no way
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for urlopen to automatically determine the encoding of the byte stream
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it receives from the http server. In general, a program will decode
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the returned bytes object to string once it determines or guesses
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the appropriate encoding.
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The following W3C document, http://www.w3.org/International/O-charset , lists
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the various ways in which a (X)HTML or a XML document could have specified its
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encoding information.
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As python.org website uses *utf-8* encoding as specified in it's meta tag, we
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will use same for decoding the bytes object. ::
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>>> import urllib.request
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>>> f = urllib.request.urlopen('http://www.python.org/')
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>>> print(fp.read(100).decode('utf-8'))
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtm
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In the following example, we are sending a data-stream to the stdin of a CGI
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and reading the data it returns to us. Note that this example will only work
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when the Python installation supports SSL. ::
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>>> import urllib.request
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>>> req = urllib.request.Request(url='https://localhost/cgi-bin/test.cgi',
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... data='This data is passed to stdin of the CGI')
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>>> f = urllib.request.urlopen(req)
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>>> print(f.read().decode('utf-8'))
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Got Data: "This data is passed to stdin of the CGI"
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The code for the sample CGI used in the above example is::
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#!/usr/bin/env python
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import sys
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data = sys.stdin.read()
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print('Content-type: text-plain\n\nGot Data: "%s"' % data)
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Use of Basic HTTP Authentication::
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import urllib.request
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# Create an OpenerDirector with support for Basic HTTP Authentication...
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auth_handler = urllib.request.HTTPBasicAuthHandler()
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auth_handler.add_password(realm='PDQ Application',
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uri='https://mahler:8092/site-updates.py',
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user='klem',
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passwd='kadidd!ehopper')
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opener = urllib.request.build_opener(auth_handler)
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# ...and install it globally so it can be used with urlopen.
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urllib.request.install_opener(opener)
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urllib.request.urlopen('http://www.example.com/login.html')
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:func:`build_opener` provides many handlers by default, including a
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:class:`ProxyHandler`. By default, :class:`ProxyHandler` uses the environment
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variables named ``<scheme>_proxy``, where ``<scheme>`` is the URL scheme
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involved. For example, the :envvar:`http_proxy` environment variable is read to
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obtain the HTTP proxy's URL.
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This example replaces the default :class:`ProxyHandler` with one that uses
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programmatically-supplied proxy URLs, and adds proxy authorization support with
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:class:`ProxyBasicAuthHandler`. ::
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proxy_handler = urllib.request.ProxyHandler({'http': 'http://www.example.com:3128/'})
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proxy_auth_handler = urllib.request.ProxyBasicAuthHandler()
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proxy_auth_handler.add_password('realm', 'host', 'username', 'password')
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opener = urllib.request.build_opener(proxy_handler, proxy_auth_handler)
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# This time, rather than install the OpenerDirector, we use it directly:
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opener.open('http://www.example.com/login.html')
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Adding HTTP headers:
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Use the *headers* argument to the :class:`Request` constructor, or::
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import urllib.request
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req = urllib.request.Request('http://www.example.com/')
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req.add_header('Referer', 'http://www.python.org/')
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r = urllib.request.urlopen(req)
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:class:`OpenerDirector` automatically adds a :mailheader:`User-Agent` header to
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every :class:`Request`. To change this::
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import urllib.request
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opener = urllib.request.build_opener()
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opener.addheaders = [('User-agent', 'Mozilla/5.0')]
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opener.open('http://www.example.com/')
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Also, remember that a few standard headers (:mailheader:`Content-Length`,
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:mailheader:`Content-Type` and :mailheader:`Host`) are added when the
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:class:`Request` is passed to :func:`urlopen` (or :meth:`OpenerDirector.open`).
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.. _urllib-examples:
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Here is an example session that uses the ``GET`` method to retrieve a URL
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containing parameters::
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>>> import urllib.request
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>>> import urllib.parse
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>>> params = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
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>>> f = urllib.request.urlopen("http://www.musi-cal.com/cgi-bin/query?%s" % params)
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>>> print(f.read().decode('utf-8'))
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The following example uses the ``POST`` method instead::
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>>> import urllib.request
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>>> import urllib.parse
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>>> params = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
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>>> f = urllib.request.urlopen("http://www.musi-cal.com/cgi-bin/query", params)
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>>> print(f.read().decode('utf-8'))
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The following example uses an explicitly specified HTTP proxy, overriding
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environment settings::
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>>> import urllib.request
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>>> proxies = {'http': 'http://proxy.example.com:8080/'}
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>>> opener = urllib.request.FancyURLopener(proxies)
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>>> f = opener.open("http://www.python.org")
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>>> f.read().decode('utf-8')
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The following example uses no proxies at all, overriding environment settings::
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>>> import urllib.request
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>>> opener = urllib.request.FancyURLopener({})
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>>> f = opener.open("http://www.python.org/")
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>>> f.read().decode('utf-8')
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:mod:`urllib.request` Restrictions
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----------------------------------
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.. index::
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pair: HTTP; protocol
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pair: FTP; protocol
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* Currently, only the following protocols are supported: HTTP, (versions 0.9 and
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1.0), FTP, and local files.
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* The caching feature of :func:`urlretrieve` has been disabled until I find the
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time to hack proper processing of Expiration time headers.
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* There should be a function to query whether a particular URL is in the cache.
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* For backward compatibility, if a URL appears to point to a local file but the
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file can't be opened, the URL is re-interpreted using the FTP protocol. This
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can sometimes cause confusing error messages.
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* The :func:`urlopen` and :func:`urlretrieve` functions can cause arbitrarily
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long delays while waiting for a network connection to be set up. This means
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that it is difficult to build an interactive Web client using these functions
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without using threads.
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.. index::
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single: HTML
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pair: HTTP; protocol
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* The data returned by :func:`urlopen` or :func:`urlretrieve` is the raw data
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returned by the server. This may be binary data (such as an image), plain text
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or (for example) HTML. The HTTP protocol provides type information in the reply
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header, which can be inspected by looking at the :mailheader:`Content-Type`
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header. If the returned data is HTML, you can use the module
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:mod:`html.parser` to parse it.
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.. index:: single: FTP
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* The code handling the FTP protocol cannot differentiate between a file and a
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directory. This can lead to unexpected behavior when attempting to read a URL
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that points to a file that is not accessible. If the URL ends in a ``/``, it is
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assumed to refer to a directory and will be handled accordingly. But if an
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attempt to read a file leads to a 550 error (meaning the URL cannot be found or
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is not accessible, often for permission reasons), then the path is treated as a
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directory in order to handle the case when a directory is specified by a URL but
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the trailing ``/`` has been left off. This can cause misleading results when
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you try to fetch a file whose read permissions make it inaccessible; the FTP
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code will try to read it, fail with a 550 error, and then perform a directory
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listing for the unreadable file. If fine-grained control is needed, consider
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using the :mod:`ftplib` module, subclassing :class:`FancyURLOpener`, or changing
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*_urlopener* to meet your needs.
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:mod:`urllib.response` --- Response classes used by urllib.
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===========================================================
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.. module:: urllib.response
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:synopsis: Response classes used by urllib.
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The :mod:`urllib.response` module defines functions and classes which define a
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minimal file like interface, including ``read()`` and ``readline()``. The
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typical response object is an addinfourl instance, which defines and ``info()``
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method and that returns headers and a ``geturl()`` method that returns the url.
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Functions defined by this module are used internally by the
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:mod:`urllib.request` module.
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