# 18.17 `urlparse` -- 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`.

New in version 2.5: Support for the `sftp` and `sips` schemes.

The `urlparse` module defines the following functions:

`urlparse`( | urlstring[, default_scheme[, allow_fragments]])

  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 urlparse import urlparse
      >>> o = urlparse('http://www.cwi.nl:80/%7Eguido/Python.html')
      >>> o
      ('http', 'www.cwi.nl:80', '/%7Eguido/Python.html', '', '', '')
      >>> 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 element | empty string
  `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 present | `None`

  See section 18.17.1, ``Results of `urlparse()` and `urlsplit()`,'' for more information on the result object.

  Changed in version 2.5: Added attributes to return value.

`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).

`urlsplit`( | urlstring[, default_scheme[, allow_fragments]])

  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, if present | `None`

  See section 18.17.1, ``Results of `urlparse()` and `urlsplit()`,'' for more information on the result object.

  New in version 2.2. Changed in version 2.5: Added attributes to return value.

`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). New in version 2.2.

`urljoin`( | base, url[, allow_fragments])

  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 urlparse 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.

`urldefrag`( | url)

  If url contains a fragment identifier, returns 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, returns url unmodified and an empty string.

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).