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Documentation updates for urllib package. Modified the documentation for the
urllib,urllib2 -> urllib.request,urllib.error urlparse -> urllib.parse RobotParser -> urllib.robotparser Updated tutorial references and other module references (http.client.rst, ftplib.rst,contextlib.rst) Updated the examples in the urllib2-howto Addresses Issue3142.
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Senthil Kumaran
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Doc/library/urllib.parse.rst
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Doc/library/urllib.parse.rst
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:mod:`urllib.parse` --- Parse URLs into components
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==================================================
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.. module:: urllib.parse
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:synopsis: Parse URLs into or assemble them from components.
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.. index::
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single: WWW
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single: World Wide Web
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single: URL
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pair: URL; parsing
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pair: relative; URL
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This module defines a standard interface to break Uniform Resource Locator (URL)
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strings up in components (addressing scheme, network location, path etc.), to
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combine the components back into a URL string, and to convert a "relative URL"
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to an absolute URL given a "base URL."
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The module has been designed to match the Internet RFC on Relative Uniform
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Resource Locators (and discovered a bug in an earlier draft!). It supports the
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following URL schemes: ``file``, ``ftp``, ``gopher``, ``hdl``, ``http``,
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``https``, ``imap``, ``mailto``, ``mms``, ``news``, ``nntp``, ``prospero``,
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``rsync``, ``rtsp``, ``rtspu``, ``sftp``, ``shttp``, ``sip``, ``sips``,
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``snews``, ``svn``, ``svn+ssh``, ``telnet``, ``wais``.
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The :mod:`urllib.parse` module defines the following functions:
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.. function:: urlparse(urlstring[, default_scheme[, allow_fragments]])
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Parse a URL into six components, returning a 6-tuple. This corresponds to the
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general structure of a URL: ``scheme://netloc/path;parameters?query#fragment``.
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Each tuple item is a string, possibly empty. The components are not broken up in
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smaller parts (for example, the network location is a single string), and %
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escapes are not expanded. The delimiters as shown above are not part of the
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result, except for a leading slash in the *path* component, which is retained if
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present. For example:
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>>> from urllib.parse import urlparse
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>>> o = urlparse('http://www.cwi.nl:80/%7Eguido/Python.html')
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>>> o # doctest: +NORMALIZE_WHITESPACE
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ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
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params='', query='', fragment='')
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>>> o.scheme
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'http'
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>>> o.port
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80
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>>> o.geturl()
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'http://www.cwi.nl:80/%7Eguido/Python.html'
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If the *default_scheme* argument is specified, it gives the default addressing
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scheme, to be used only if the URL does not specify one. The default value for
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this argument is the empty string.
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If the *allow_fragments* argument is false, fragment identifiers are not
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allowed, even if the URL's addressing scheme normally does support them. The
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default value for this argument is :const:`True`.
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The return value is actually an instance of a subclass of :class:`tuple`. This
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class has the following additional read-only convenience attributes:
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+------------------+-------+--------------------------+----------------------+
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| Attribute | Index | Value | Value if not present |
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+==================+=======+==========================+======================+
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| :attr:`scheme` | 0 | URL scheme specifier | empty string |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`netloc` | 1 | Network location part | empty string |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`path` | 2 | Hierarchical path | empty string |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`params` | 3 | Parameters for last path | empty string |
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| | | element | |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`query` | 4 | Query component | empty string |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`fragment` | 5 | Fragment identifier | empty string |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`username` | | User name | :const:`None` |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`password` | | Password | :const:`None` |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`hostname` | | Host name (lower case) | :const:`None` |
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+------------------+-------+--------------------------+----------------------+
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| :attr:`port` | | Port number as integer, | :const:`None` |
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| | | if present | |
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+------------------+-------+--------------------------+----------------------+
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See section :ref:`urlparse-result-object` for more information on the result
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object.
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.. function:: urlunparse(parts)
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Construct a URL from a tuple as returned by ``urlparse()``. The *parts* argument
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can be any six-item iterable. This may result in a slightly different, but
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equivalent URL, if the URL that was parsed originally had unnecessary delimiters
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(for example, a ? with an empty query; the RFC states that these are
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equivalent).
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.. function:: urlsplit(urlstring[, default_scheme[, allow_fragments]])
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This is similar to :func:`urlparse`, but does not split the params from the URL.
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This should generally be used instead of :func:`urlparse` if the more recent URL
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syntax allowing parameters to be applied to each segment of the *path* portion
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of the URL (see :rfc:`2396`) is wanted. A separate function is needed to
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separate the path segments and parameters. This function returns a 5-tuple:
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(addressing scheme, network location, path, query, fragment identifier).
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The return value is actually an instance of a subclass of :class:`tuple`. This
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class has the following additional read-only convenience attributes:
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+------------------+-------+-------------------------+----------------------+
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| Attribute | Index | Value | Value if not present |
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+==================+=======+=========================+======================+
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| :attr:`scheme` | 0 | URL scheme specifier | empty string |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`netloc` | 1 | Network location part | empty string |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`path` | 2 | Hierarchical path | empty string |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`query` | 3 | Query component | empty string |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`fragment` | 4 | Fragment identifier | empty string |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`username` | | User name | :const:`None` |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`password` | | Password | :const:`None` |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`hostname` | | Host name (lower case) | :const:`None` |
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+------------------+-------+-------------------------+----------------------+
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| :attr:`port` | | Port number as integer, | :const:`None` |
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| | | if present | |
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+------------------+-------+-------------------------+----------------------+
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See section :ref:`urlparse-result-object` for more information on the result
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object.
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.. function:: urlunsplit(parts)
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Combine the elements of a tuple as returned by :func:`urlsplit` into a complete
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URL as a string. The *parts* argument can be any five-item iterable. This may
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result in a slightly different, but equivalent URL, if the URL that was parsed
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originally had unnecessary delimiters (for example, a ? with an empty query; the
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RFC states that these are equivalent).
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.. function:: urljoin(base, url[, allow_fragments])
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Construct a full ("absolute") URL by combining a "base URL" (*base*) with
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another URL (*url*). Informally, this uses components of the base URL, in
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particular the addressing scheme, the network location and (part of) the path,
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to provide missing components in the relative URL. For example:
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>>> from urllib.parse import urljoin
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>>> urljoin('http://www.cwi.nl/%7Eguido/Python.html', 'FAQ.html')
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'http://www.cwi.nl/%7Eguido/FAQ.html'
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The *allow_fragments* argument has the same meaning and default as for
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:func:`urlparse`.
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.. note::
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If *url* is an absolute URL (that is, starting with ``//`` or ``scheme://``),
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the *url*'s host name and/or scheme will be present in the result. For example:
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.. doctest::
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>>> urljoin('http://www.cwi.nl/%7Eguido/Python.html',
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... '//www.python.org/%7Eguido')
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'http://www.python.org/%7Eguido'
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If you do not want that behavior, preprocess the *url* with :func:`urlsplit` and
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:func:`urlunsplit`, removing possible *scheme* and *netloc* parts.
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.. function:: urldefrag(url)
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If *url* contains a fragment identifier, returns a modified version of *url*
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with no fragment identifier, and the fragment identifier as a separate string.
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If there is no fragment identifier in *url*, returns *url* unmodified and an
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empty string.
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.. function:: quote(string[, safe])
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Replace special characters in *string* using the ``%xx`` escape. Letters,
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digits, and the characters ``'_.-'`` are never quoted. The optional *safe*
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parameter specifies additional characters that should not be quoted --- its
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default value is ``'/'``.
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Example: ``quote('/~connolly/')`` yields ``'/%7econnolly/'``.
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.. function:: quote_plus(string[, safe])
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Like :func:`quote`, but also replaces spaces by plus signs, as required for
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quoting HTML form values. Plus signs in the original string are escaped unless
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they are included in *safe*. It also does not have *safe* default to ``'/'``.
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.. function:: unquote(string)
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Replace ``%xx`` escapes by their single-character equivalent.
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Example: ``unquote('/%7Econnolly/')`` yields ``'/~connolly/'``.
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.. function:: unquote_plus(string)
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Like :func:`unquote`, but also replaces plus signs by spaces, as required for
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unquoting HTML form values.
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.. function:: urlencode(query[, doseq])
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Convert a mapping object or a sequence of two-element tuples to a "url-encoded"
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string, suitable to pass to :func:`urlopen` above as the optional *data*
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argument. This is useful to pass a dictionary of form fields to a ``POST``
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request. The resulting string is a series of ``key=value`` pairs separated by
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``'&'`` characters, where both *key* and *value* are quoted using
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:func:`quote_plus` above. If the optional parameter *doseq* is present and
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evaluates to true, individual ``key=value`` pairs are generated for each element
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of the sequence. When a sequence of two-element tuples is used as the *query*
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argument, the first element of each tuple is a key and the second is a value.
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The order of parameters in the encoded string will match the order of parameter
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tuples in the sequence. The :mod:`cgi` module provides the functions
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:func:`parse_qs` and :func:`parse_qsl` which are used to parse query strings
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into Python data structures.
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.. seealso::
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:rfc:`1738` - Uniform Resource Locators (URL)
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This specifies the formal syntax and semantics of absolute URLs.
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:rfc:`1808` - Relative Uniform Resource Locators
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This Request For Comments includes the rules for joining an absolute and a
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relative URL, including a fair number of "Abnormal Examples" which govern the
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treatment of border cases.
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:rfc:`2396` - Uniform Resource Identifiers (URI): Generic Syntax
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Document describing the generic syntactic requirements for both Uniform Resource
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Names (URNs) and Uniform Resource Locators (URLs).
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.. _urlparse-result-object:
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Results of :func:`urlparse` and :func:`urlsplit`
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------------------------------------------------
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The result objects from the :func:`urlparse` and :func:`urlsplit` functions are
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subclasses of the :class:`tuple` type. These subclasses add the attributes
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described in those functions, as well as provide an additional method:
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.. method:: ParseResult.geturl()
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Return the re-combined version of the original URL as a string. This may differ
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from the original URL in that the scheme will always be normalized to lower case
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and empty components may be dropped. Specifically, empty parameters, queries,
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and fragment identifiers will be removed.
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The result of this method is a fixpoint if passed back through the original
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parsing function:
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>>> import urllib.parse
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>>> url = 'HTTP://www.Python.org/doc/#'
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>>> r1 = urllib.parse.urlsplit(url)
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>>> r1.geturl()
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'http://www.Python.org/doc/'
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>>> r2 = urllib.parse.urlsplit(r1.geturl())
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>>> r2.geturl()
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'http://www.Python.org/doc/'
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The following classes provide the implementations of the parse results::
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.. class:: BaseResult
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Base class for the concrete result classes. This provides most of the attribute
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definitions. It does not provide a :meth:`geturl` method. It is derived from
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:class:`tuple`, but does not override the :meth:`__init__` or :meth:`__new__`
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methods.
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.. class:: ParseResult(scheme, netloc, path, params, query, fragment)
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Concrete class for :func:`urlparse` results. The :meth:`__new__` method is
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overridden to support checking that the right number of arguments are passed.
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.. class:: SplitResult(scheme, netloc, path, query, fragment)
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Concrete class for :func:`urlsplit` results. The :meth:`__new__` method is
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overridden to support checking that the right number of arguments are passed.
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