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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. + |