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cpython/Doc/library/urllib.request.rst
Georg Brandl 7fe2c4af0e #4355: refer to urlencode in the correct module.
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: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.parse.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.parse.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:`urllib`'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:`HTTPDefaultErrorHandler` will raise an
:exc:`HTTPError` if no other handler handles the error.
.. _urllib-request-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
programmatically-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.request
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.request
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.
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