
``urllib.parse`` --- Parse URLs into components
***********************************************

This module defines a standard interface to break Uniform Resource
Locator (URL) strings up in components (addressing scheme, network
location, path etc.), to combine the components back into a URL
string, and to convert a "relative URL" to an absolute URL given a
"base URL."

The module has been designed to match the Internet RFC on Relative
Uniform Resource Locators (and discovered a bug in an earlier draft!).
It supports the following URL schemes: ``file``, ``ftp``, ``gopher``,
``hdl``, ``http``, ``https``, ``imap``, ``mailto``, ``mms``, ``news``,
``nntp``, ``prospero``, ``rsync``, ``rtsp``, ``rtspu``, ``sftp``,
``shttp``, ``sip``, ``sips``, ``snews``, ``svn``, ``svn+ssh``,
``telnet``, ``wais``.

The ``urllib.parse`` module defines the following functions:

urllib.parse.urlparse(urlstring, default_scheme='', allow_fragments=True)

   Parse a URL into six components, returning a 6-tuple.  This
   corresponds to the general structure of a URL:
   ``scheme://netloc/path;parameters?query#fragment``. Each tuple item
   is a string, possibly empty. The components are not broken up in
   smaller parts (for example, the network location is a single
   string), and % escapes are not expanded. The delimiters as shown
   above are not part of the result, except for a leading slash in the
   *path* component, which is retained if present.  For example:

   >>> from urllib.parse import urlparse
   >>> o = urlparse('http://www.cwi.nl:80/%7Eguido/Python.html')
   >>> o   # doctest: +NORMALIZE_WHITESPACE
   ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
               params='', query='', fragment='')
   >>> o.scheme
   'http'
   >>> o.port
   80
   >>> o.geturl()
   'http://www.cwi.nl:80/%7Eguido/Python.html'

   If the *default_scheme* argument is specified, it gives the default
   addressing scheme, to be used only if the URL does not specify one.
   The default value for this argument is the empty string.

   If the *allow_fragments* argument is false, fragment identifiers
   are not allowed, even if the URL's addressing scheme normally does
   support them.  The default value for this argument is ``True``.

   The return value is actually an instance of a subclass of
   ``tuple``.  This class has the following additional read-only
   convenience attributes:

   +--------------------+---------+----------------------------+------------------------+
   | Attribute          | Index   | Value                      | Value if not present   |
   +====================+=========+============================+========================+
   | ``scheme``         | 0       | URL scheme specifier       | empty string           |
   +--------------------+---------+----------------------------+------------------------+
   | ``netloc``         | 1       | Network location part      | empty string           |
   +--------------------+---------+----------------------------+------------------------+
   | ``path``           | 2       | Hierarchical path          | empty string           |
   +--------------------+---------+----------------------------+------------------------+
   | ``params``         | 3       | Parameters for last path   | empty string           |
   |                    |         | element                    |                        |
   +--------------------+---------+----------------------------+------------------------+
   | ``query``          | 4       | Query component            | empty string           |
   +--------------------+---------+----------------------------+------------------------+
   | ``fragment``       | 5       | Fragment identifier        | empty string           |
   +--------------------+---------+----------------------------+------------------------+
   | ``username``       |         | User name                  | ``None``               |
   +--------------------+---------+----------------------------+------------------------+
   | ``password``       |         | Password                   | ``None``               |
   +--------------------+---------+----------------------------+------------------------+
   | ``hostname``       |         | Host name (lower case)     | ``None``               |
   +--------------------+---------+----------------------------+------------------------+
   | ``port``           |         | Port number as integer, if | ``None``               |
   |                    |         | present                    |                        |
   +--------------------+---------+----------------------------+------------------------+

   See section *Results of urlparse() and urlsplit()* for more
   information on the result object.

urllib.parse.parse_qs(qs, keep_blank_values=False, strict_parsing=False)

   Parse a query string given as a string argument (data of type
   *application/x-www-form-urlencoded*).  Data are returned as a
   dictionary.  The dictionary keys are the unique query variable
   names and the values are lists of values for each name.

   The optional argument *keep_blank_values* is a flag indicating
   whether blank values in URL encoded queries should be treated as
   blank strings.   A true value indicates that blanks should be
   retained as  blank strings.  The default false value indicates that
   blank values are to be ignored and treated as if they were not
   included.

   The optional argument *strict_parsing* is a flag indicating what to
   do with parsing errors.  If false (the default), errors are
   silently ignored.  If true, errors raise a ``ValueError``
   exception.

   Use the ``urllib.parse.urlencode()`` function to convert such
   dictionaries into query strings.

urllib.parse.parse_qsl(qs, keep_blank_values=False, strict_parsing=False)

   Parse a query string given as a string argument (data of type
   *application/x-www-form-urlencoded*).  Data are returned as a list
   of name, value pairs.

   The optional argument *keep_blank_values* is a flag indicating
   whether blank values in URL encoded queries should be treated as
   blank strings.   A true value indicates that blanks should be
   retained as  blank strings.  The default false value indicates that
   blank values are to be ignored and treated as if they were not
   included.

   The optional argument *strict_parsing* is a flag indicating what to
   do with parsing errors.  If false (the default), errors are
   silently ignored.  If true, errors raise a ``ValueError``
   exception.

   Use the ``urllib.parse.urlencode()`` function to convert such lists
   of pairs into query strings.

urllib.parse.urlunparse(parts)

   Construct a URL from a tuple as returned by ``urlparse()``. The
   *parts* argument can be any six-item iterable. This may result in a
   slightly different, but equivalent URL, if the URL that was parsed
   originally had unnecessary delimiters (for example, a ``?`` with an
   empty query; the RFC states that these are equivalent).

urllib.parse.urlsplit(urlstring, default_scheme='', allow_fragments=True)

   This is similar to ``urlparse()``, but does not split the params
   from the URL. This should generally be used instead of
   ``urlparse()`` if the more recent URL syntax allowing parameters to
   be applied to each segment of the *path* portion of the URL (see
   **RFC 2396**) is wanted.  A separate function is needed to separate
   the path segments and parameters.  This function returns a 5-tuple:
   (addressing scheme, network location, path, query, fragment
   identifier).

   The return value is actually an instance of a subclass of
   ``tuple``.  This class has the following additional read-only
   convenience attributes:

   +--------------------+---------+---------------------------+------------------------+
   | Attribute          | Index   | Value                     | Value if not present   |
   +====================+=========+===========================+========================+
   | ``scheme``         | 0       | URL scheme specifier      | empty string           |
   +--------------------+---------+---------------------------+------------------------+
   | ``netloc``         | 1       | Network location part     | empty string           |
   +--------------------+---------+---------------------------+------------------------+
   | ``path``           | 2       | Hierarchical path         | empty string           |
   +--------------------+---------+---------------------------+------------------------+
   | ``query``          | 3       | Query component           | empty string           |
   +--------------------+---------+---------------------------+------------------------+
   | ``fragment``       | 4       | Fragment identifier       | empty string           |
   +--------------------+---------+---------------------------+------------------------+
   | ``username``       |         | User name                 | ``None``               |
   +--------------------+---------+---------------------------+------------------------+
   | ``password``       |         | Password                  | ``None``               |
   +--------------------+---------+---------------------------+------------------------+
   | ``hostname``       |         | Host name (lower case)    | ``None``               |
   +--------------------+---------+---------------------------+------------------------+
   | ``port``           |         | Port number as integer,   | ``None``               |
   |                    |         | if present                |                        |
   +--------------------+---------+---------------------------+------------------------+

   See section *Results of urlparse() and urlsplit()* for more
   information on the result object.

urllib.parse.urlunsplit(parts)

   Combine the elements of a tuple as returned by ``urlsplit()`` into
   a complete URL as a string. The *parts* argument can be any five-
   item iterable. This may result in a slightly different, but
   equivalent URL, if the URL that was parsed originally had
   unnecessary delimiters (for example, a ? with an empty query; the
   RFC states that these are equivalent).

urllib.parse.urljoin(base, url, allow_fragments=True)

   Construct a full ("absolute") URL by combining a "base URL"
   (*base*) with another URL (*url*).  Informally, this uses
   components of the base URL, in particular the addressing scheme,
   the network location and (part of) the path, to provide missing
   components in the relative URL.  For example:

   >>> from urllib.parse import urljoin
   >>> urljoin('http://www.cwi.nl/%7Eguido/Python.html', 'FAQ.html')
   'http://www.cwi.nl/%7Eguido/FAQ.html'

   The *allow_fragments* argument has the same meaning and default as
   for ``urlparse()``.

   Note: If *url* is an absolute URL (that is, starting with ``//`` or
     ``scheme://``), the *url*'s host name and/or scheme will be
     present in the result.  For example:

      >>> urljoin('http://www.cwi.nl/%7Eguido/Python.html',
      ...         '//www.python.org/%7Eguido')
      'http://www.python.org/%7Eguido'

   If you do not want that behavior, preprocess the *url* with
   ``urlsplit()`` and ``urlunsplit()``, removing possible *scheme* and
   *netloc* parts.

urllib.parse.urldefrag(url)

   If *url* contains a fragment identifier, return a modified version
   of *url* with no fragment identifier, and the fragment identifier
   as a separate string.  If there is no fragment identifier in *url*,
   return *url* unmodified and an empty string.

urllib.parse.quote(string, safe='/', encoding=None, errors=None)

   Replace special characters in *string* using the ``%xx`` escape.
   Letters, digits, and the characters ``'_.-'`` are never quoted. By
   default, this function is intended for quoting the path section of
   URL. The optional *safe* parameter specifies additional ASCII
   characters that should not be quoted --- its default value is
   ``'/'``.

   *string* may be either a ``str`` or a ``bytes``.

   The optional *encoding* and *errors* parameters specify how to deal
   with non-ASCII characters, as accepted by the ``str.encode()``
   method. *encoding* defaults to ``'utf-8'``. *errors* defaults to
   ``'strict'``, meaning unsupported characters raise a
   ``UnicodeEncodeError``. *encoding* and *errors* must not be
   supplied if *string* is a ``bytes``, or a ``TypeError`` is raised.

   Note that ``quote(string, safe, encoding, errors)`` is equivalent
   to ``quote_from_bytes(string.encode(encoding, errors), safe)``.

   Example: ``quote('/El Niño/')`` yields ``'/El%20Ni%C3%B1o/'``.

urllib.parse.quote_plus(string, safe='', encoding=None, errors=None)

   Like ``quote()``, but also replace spaces by plus signs, as
   required for quoting HTML form values when building up a query
   string to go into a URL. Plus signs in the original string are
   escaped unless they are included in *safe*.  It also does not have
   *safe* default to ``'/'``.

   Example: ``quote_plus('/El Niño/')`` yields
   ``'%2FEl+Ni%C3%B1o%2F'``.

urllib.parse.quote_from_bytes(bytes, safe='/')

   Like ``quote()``, but accepts a ``bytes`` object rather than a
   ``str``, and does not perform string-to-bytes encoding.

   Example: ``quote_from_bytes(b'a&\xef')`` yields ``'a%26%EF'``.

urllib.parse.unquote(string, encoding='utf-8', errors='replace')

   Replace ``%xx`` escapes by their single-character equivalent. The
   optional *encoding* and *errors* parameters specify how to decode
   percent-encoded sequences into Unicode characters, as accepted by
   the ``bytes.decode()`` method.

   *string* must be a ``str``.

   *encoding* defaults to ``'utf-8'``. *errors* defaults to
   ``'replace'``, meaning invalid sequences are replaced by a
   placeholder character.

   Example: ``unquote('/El%20Ni%C3%B1o/')`` yields ``'/El Niño/'``.

urllib.parse.unquote_plus(string, encoding='utf-8', errors='replace')

   Like ``unquote()``, but also replace plus signs by spaces, as
   required for unquoting HTML form values.

   *string* must be a ``str``.

   Example: ``unquote_plus('/El+Ni%C3%B1o/')`` yields ``'/El Niño/'``.

urllib.parse.unquote_to_bytes(string)

   Replace ``%xx`` escapes by their single-octet equivalent, and
   return a ``bytes`` object.

   *string* may be either a ``str`` or a ``bytes``.

   If it is a ``str``, unescaped non-ASCII characters in *string* are
   encoded into UTF-8 bytes.

   Example: ``unquote_to_bytes('a%26%EF')`` yields ``b'a&\xef'``.

urllib.parse.urlencode(query, doseq=False)

   Convert a mapping object or a sequence of two-element tuples  to a
   "url-encoded" string, suitable to pass to ``urlopen()`` above as
   the optional *data* argument.  This is useful to pass a dictionary
   of form fields to a ``POST`` request.  The resulting string is a
   series of ``key=value`` pairs separated by ``'&'`` characters,
   where both *key* and *value* are quoted using ``quote_plus()``
   above.  If the optional parameter *doseq* is present and evaluates
   to true, individual ``key=value`` pairs are generated for each
   element of the sequence. When a sequence of two-element tuples is
   used as the *query* argument, the first element of each tuple is a
   key and the second is a value. The order of parameters in the
   encoded string will match the order of parameter tuples in the
   sequence. This module provides the functions ``parse_qs()`` and
   ``parse_qsl()`` which are used to parse query strings into Python
   data structures.

See also:

   **RFC 1738** - Uniform Resource Locators (URL)
      This specifies the formal syntax and semantics of absolute URLs.

   **RFC 1808** - Relative Uniform Resource Locators
      This Request For Comments includes the rules for joining an
      absolute and a relative URL, including a fair number of
      "Abnormal Examples" which govern the treatment of border cases.

   **RFC 2396** - Uniform Resource Identifiers (URI): Generic Syntax
      Document describing the generic syntactic requirements for both
      Uniform Resource Names (URNs) and Uniform Resource Locators
      (URLs).


Results of ``urlparse()`` and ``urlsplit()``
============================================

The result objects from the ``urlparse()`` and ``urlsplit()``
functions are subclasses of the ``tuple`` type.  These subclasses add
the attributes described in those functions, as well as provide an
additional method:

ParseResult.geturl()

   Return the re-combined version of the original URL as a string.
   This may differ from the original URL in that the scheme will
   always be normalized to lower case and empty components may be
   dropped. Specifically, empty parameters, queries, and fragment
   identifiers will be removed.

   The result of this method is a fixpoint if passed back through the
   original parsing function:

      >>> import urllib.parse
      >>> url = 'HTTP://www.Python.org/doc/#'

      >>> r1 = urllib.parse.urlsplit(url)
      >>> r1.geturl()
      'http://www.Python.org/doc/'

      >>> r2 = urllib.parse.urlsplit(r1.geturl())
      >>> r2.geturl()
      'http://www.Python.org/doc/'

The following classes provide the implementations of the parse
results:

class class urllib.parse.BaseResult

   Base class for the concrete result classes.  This provides most of
   the attribute definitions.  It does not provide a ``geturl()``
   method.  It is derived from ``tuple``, but does not override the
   ``__init__()`` or ``__new__()`` methods.

class class urllib.parse.ParseResult(scheme, netloc, path, params, query, fragment)

   Concrete class for ``urlparse()`` results.  The ``__new__()``
   method is overridden to support checking that the right number of
   arguments are passed.

class class urllib.parse.SplitResult(scheme, netloc, path, query, fragment)

   Concrete class for ``urlsplit()`` results.  The ``__new__()``
   method is overridden to support checking that the right number of
   arguments are passed.
