/Doc/library/urlparse.rst

  1:mod:`urlparse` --- Parse URLs into components
  2==============================================
  3
  4.. module:: urlparse
  5   :synopsis: Parse URLs into or assemble them from components.
  6
  7
  8.. index::
  9   single: WWW
 10   single: World Wide Web
 11   single: URL
 12   pair: URL; parsing
 13   pair: relative; URL
 14
 15.. note::
 16   The :mod:`urlparse` module is renamed to :mod:`urllib.parse` in Python 3.0.
 17   The :term:`2to3` tool will automatically adapt imports when converting
 18   your sources to 3.0.
 19
 20
 21This module defines a standard interface to break Uniform Resource Locator (URL)
 22strings up in components (addressing scheme, network location, path etc.), to
 23combine the components back into a URL string, and to convert a "relative URL"
 24to an absolute URL given a "base URL."
 25
 26The module has been designed to match the Internet RFC on Relative Uniform
 27Resource Locators (and discovered a bug in an earlier draft!). It supports the
 28following URL schemes: ``file``, ``ftp``, ``gopher``, ``hdl``, ``http``,
 29``https``, ``imap``, ``mailto``, ``mms``, ``news``,  ``nntp``, ``prospero``,
 30``rsync``, ``rtsp``, ``rtspu``,  ``sftp``, ``shttp``, ``sip``, ``sips``,
 31``snews``, ``svn``,  ``svn+ssh``, ``telnet``, ``wais``.
 32
 33.. versionadded:: 2.5
 34   Support for the ``sftp`` and ``sips`` schemes.
 35
 36The :mod:`urlparse` module defines the following functions:
 37
 38
 39.. function:: urlparse(urlstring[, default_scheme[, allow_fragments]])
 40
 41   Parse a URL into six components, returning a 6-tuple.  This corresponds to the
 42   general structure of a URL: ``scheme://netloc/path;parameters?query#fragment``.
 43   Each tuple item is a string, possibly empty. The components are not broken up in
 44   smaller parts (for example, the network location is a single string), and %
 45   escapes are not expanded. The delimiters as shown above are not part of the
 46   result, except for a leading slash in the *path* component, which is retained if
 47   present.  For example:
 48
 49      >>> from urlparse import urlparse
 50      >>> o = urlparse('http://www.cwi.nl:80/%7Eguido/Python.html')
 51      >>> o   # doctest: +NORMALIZE_WHITESPACE
 52      ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
 53                  params='', query='', fragment='')
 54      >>> o.scheme
 55      'http'
 56      >>> o.port
 57      80
 58      >>> o.geturl()
 59      'http://www.cwi.nl:80/%7Eguido/Python.html'
 60
 61   If the *default_scheme* argument is specified, it gives the default addressing
 62   scheme, to be used only if the URL does not specify one.  The default value for
 63   this argument is the empty string.
 64
 65   If the *allow_fragments* argument is false, fragment identifiers are not
 66   allowed, even if the URL's addressing scheme normally does support them.  The
 67   default value for this argument is :const:`True`.
 68
 69   The return value is actually an instance of a subclass of :class:`tuple`.  This
 70   class has the following additional read-only convenience attributes:
 71
 72   +------------------+-------+--------------------------+----------------------+
 73   | Attribute        | Index | Value                    | Value if not present |
 74   +==================+=======+==========================+======================+
 75   | :attr:`scheme`   | 0     | URL scheme specifier     | empty string         |
 76   +------------------+-------+--------------------------+----------------------+
 77   | :attr:`netloc`   | 1     | Network location part    | empty string         |
 78   +------------------+-------+--------------------------+----------------------+
 79   | :attr:`path`     | 2     | Hierarchical path        | empty string         |
 80   +------------------+-------+--------------------------+----------------------+
 81   | :attr:`params`   | 3     | Parameters for last path | empty string         |
 82   |                  |       | element                  |                      |
 83   +------------------+-------+--------------------------+----------------------+
 84   | :attr:`query`    | 4     | Query component          | empty string         |
 85   +------------------+-------+--------------------------+----------------------+
 86   | :attr:`fragment` | 5     | Fragment identifier      | empty string         |
 87   +------------------+-------+--------------------------+----------------------+
 88   | :attr:`username` |       | User name                | :const:`None`        |
 89   +------------------+-------+--------------------------+----------------------+
 90   | :attr:`password` |       | Password                 | :const:`None`        |
 91   +------------------+-------+--------------------------+----------------------+
 92   | :attr:`hostname` |       | Host name (lower case)   | :const:`None`        |
 93   +------------------+-------+--------------------------+----------------------+
 94   | :attr:`port`     |       | Port number as integer,  | :const:`None`        |
 95   |                  |       | if present               |                      |
 96   +------------------+-------+--------------------------+----------------------+
 97
 98   See section :ref:`urlparse-result-object` for more information on the result
 99   object.
100
101   .. versionchanged:: 2.5
102      Added attributes to return value.
103
104.. function:: parse_qs(qs[, keep_blank_values[, strict_parsing]])
105
106   Parse a query string given as a string argument (data of type
107   :mimetype:`application/x-www-form-urlencoded`).  Data are returned as a
108   dictionary.  The dictionary keys are the unique query variable names and the
109   values are lists of values for each name.
110
111   The optional argument *keep_blank_values* is a flag indicating whether blank
112   values in URL encoded queries should be treated as blank strings.   A true value
113   indicates that blanks should be retained as  blank strings.  The default false
114   value indicates that blank values are to be ignored and treated as if they were
115   not included.
116
117   The optional argument *strict_parsing* is a flag indicating what to do with
118   parsing errors.  If false (the default), errors are silently ignored.  If true,
119   errors raise a :exc:`ValueError` exception.
120
121   Use the :func:`urllib.urlencode` function to convert such dictionaries into
122   query strings.
123
124
125.. function:: parse_qsl(qs[, keep_blank_values[, strict_parsing]])
126
127   Parse a query string given as a string argument (data of type
128   :mimetype:`application/x-www-form-urlencoded`).  Data are returned as a list of
129   name, value pairs.
130
131   The optional argument *keep_blank_values* is a flag indicating whether blank
132   values in URL encoded queries should be treated as blank strings.   A true value
133   indicates that blanks should be retained as  blank strings.  The default false
134   value indicates that blank values are to be ignored and treated as if they were
135   not included.
136
137   The optional argument *strict_parsing* is a flag indicating what to do with
138   parsing errors.  If false (the default), errors are silently ignored.  If true,
139   errors raise a :exc:`ValueError` exception.
140
141   Use the :func:`urllib.urlencode` function to convert such lists of pairs into
142   query strings.
143
144.. function:: urlunparse(parts)
145
146   Construct a URL from a tuple as returned by ``urlparse()``. The *parts* argument
147   can be any six-item iterable. This may result in a slightly different, but
148   equivalent URL, if the URL that was parsed originally had unnecessary delimiters
149   (for example, a ? with an empty query; the RFC states that these are
150   equivalent).
151
152
153.. function:: urlsplit(urlstring[, default_scheme[, allow_fragments]])
154
155   This is similar to :func:`urlparse`, but does not split the params from the URL.
156   This should generally be used instead of :func:`urlparse` if the more recent URL
157   syntax allowing parameters to be applied to each segment of the *path* portion
158   of the URL (see :rfc:`2396`) is wanted.  A separate function is needed to
159   separate the path segments and parameters.  This function returns a 5-tuple:
160   (addressing scheme, network location, path, query, fragment identifier).
161
162   The return value is actually an instance of a subclass of :class:`tuple`.  This
163   class has the following additional read-only convenience attributes:
164
165   +------------------+-------+-------------------------+----------------------+
166   | Attribute        | Index | Value                   | Value if not present |
167   +==================+=======+=========================+======================+
168   | :attr:`scheme`   | 0     | URL scheme specifier    | empty string         |
169   +------------------+-------+-------------------------+----------------------+
170   | :attr:`netloc`   | 1     | Network location part   | empty string         |
171   +------------------+-------+-------------------------+----------------------+
172   | :attr:`path`     | 2     | Hierarchical path       | empty string         |
173   +------------------+-------+-------------------------+----------------------+
174   | :attr:`query`    | 3     | Query component         | empty string         |
175   +------------------+-------+-------------------------+----------------------+
176   | :attr:`fragment` | 4     | Fragment identifier     | empty string         |
177   +------------------+-------+-------------------------+----------------------+
178   | :attr:`username` |       | User name               | :const:`None`        |
179   +------------------+-------+-------------------------+----------------------+
180   | :attr:`password` |       | Password                | :const:`None`        |
181   +------------------+-------+-------------------------+----------------------+
182   | :attr:`hostname` |       | Host name (lower case)  | :const:`None`        |
183   +------------------+-------+-------------------------+----------------------+
184   | :attr:`port`     |       | Port number as integer, | :const:`None`        |
185   |                  |       | if present              |                      |
186   +------------------+-------+-------------------------+----------------------+
187
188   See section :ref:`urlparse-result-object` for more information on the result
189   object.
190
191   .. versionadded:: 2.2
192
193   .. versionchanged:: 2.5
194      Added attributes to return value.
195
196
197.. function:: urlunsplit(parts)
198
199   Combine the elements of a tuple as returned by :func:`urlsplit` into a complete
200   URL as a string. The *parts* argument can be any five-item iterable. This may
201   result in a slightly different, but equivalent URL, if the URL that was parsed
202   originally had unnecessary delimiters (for example, a ? with an empty query; the
203   RFC states that these are equivalent).
204
205   .. versionadded:: 2.2
206
207
208.. function:: urljoin(base, url[, allow_fragments])
209
210   Construct a full ("absolute") URL by combining a "base URL" (*base*) with
211   another URL (*url*).  Informally, this uses components of the base URL, in
212   particular the addressing scheme, the network location and (part of) the path,
213   to provide missing components in the relative URL.  For example:
214
215      >>> from urlparse import urljoin
216      >>> urljoin('http://www.cwi.nl/%7Eguido/Python.html', 'FAQ.html')
217      'http://www.cwi.nl/%7Eguido/FAQ.html'
218
219   The *allow_fragments* argument has the same meaning and default as for
220   :func:`urlparse`.
221
222   .. note::
223
224      If *url* is an absolute URL (that is, starting with ``//`` or ``scheme://``),
225      the *url*'s host name and/or scheme will be present in the result.  For example:
226
227   .. doctest::
228
229      >>> urljoin('http://www.cwi.nl/%7Eguido/Python.html',
230      ...         '//www.python.org/%7Eguido')
231      'http://www.python.org/%7Eguido'
232
233   If you do not want that behavior, preprocess the *url* with :func:`urlsplit` and
234   :func:`urlunsplit`, removing possible *scheme* and *netloc* parts.
235
236
237.. function:: urldefrag(url)
238
239   If *url* contains a fragment identifier, returns a modified version of *url*
240   with no fragment identifier, and the fragment identifier as a separate string.
241   If there is no fragment identifier in *url*, returns *url* unmodified and an
242   empty string.
243
244
245.. seealso::
246
247   :rfc:`1738` - Uniform Resource Locators (URL)
248      This specifies the formal syntax and semantics of absolute URLs.
249
250   :rfc:`1808` - Relative Uniform Resource Locators
251      This Request For Comments includes the rules for joining an absolute and a
252      relative URL, including a fair number of "Abnormal Examples" which govern the
253      treatment of border cases.
254
255   :rfc:`2396` - Uniform Resource Identifiers (URI): Generic Syntax
256      Document describing the generic syntactic requirements for both Uniform Resource
257      Names (URNs) and Uniform Resource Locators (URLs).
258
259
260.. _urlparse-result-object:
261
262Results of :func:`urlparse` and :func:`urlsplit`
263------------------------------------------------
264
265The result objects from the :func:`urlparse` and :func:`urlsplit` functions are
266subclasses of the :class:`tuple` type.  These subclasses add the attributes
267described in those functions, as well as provide an additional method:
268
269
270.. method:: ParseResult.geturl()
271
272   Return the re-combined version of the original URL as a string. This may differ
273   from the original URL in that the scheme will always be normalized to lower case
274   and empty components may be dropped. Specifically, empty parameters, queries,
275   and fragment identifiers will be removed.
276
277   The result of this method is a fixpoint if passed back through the original
278   parsing function:
279
280      >>> import urlparse
281      >>> url = 'HTTP://www.Python.org/doc/#'
282
283      >>> r1 = urlparse.urlsplit(url)
284      >>> r1.geturl()
285      'http://www.Python.org/doc/'
286
287      >>> r2 = urlparse.urlsplit(r1.geturl())
288      >>> r2.geturl()
289      'http://www.Python.org/doc/'
290
291   .. versionadded:: 2.5
292
293The following classes provide the implementations of the parse results:
294
295
296.. class:: BaseResult
297
298   Base class for the concrete result classes.  This provides most of the attribute
299   definitions.  It does not provide a :meth:`geturl` method.  It is derived from
300   :class:`tuple`, but does not override the :meth:`__init__` or :meth:`__new__`
301   methods.
302
303
304.. class:: ParseResult(scheme, netloc, path, params, query, fragment)
305
306   Concrete class for :func:`urlparse` results.  The :meth:`__new__` method is
307   overridden to support checking that the right number of arguments are passed.
308
309
310.. class:: SplitResult(scheme, netloc, path, query, fragment)
311
312   Concrete class for :func:`urlsplit` results.  The :meth:`__new__` method is
313   overridden to support checking that the right number of arguments are passed.
314