This module provides regular expressions according to RFC 3986 "Uniform Resource Identifier (URI): Generic Syntax" <http://tools.ietf.org/html/rfc3986>_ and RFC 3987 "Internationalized Resource Identifiers (IRIs)" <http://tools.ietf.org/html/rfc3987>_, and
utilities for composition and relative resolution of references.

API

match (string, rule='IRI_reference')
Convenience function for checking if string matches a specific rule.

Returns a match object or None::

    >>> assert match('%C7X', 'pct_encoded') is None
    >>> assert match('%C7', 'pct_encoded')
    >>> assert match('%c7', 'pct_encoded')

parse (string, rule='IRI_reference')
Parses string according to rule into a dict of subcomponents.

If `rule` is None, parse an IRI_reference `without validation
<http://tools.ietf.org/html/rfc3986#appendix-B>`_.

If regex_ is available, any rule is supported; with re_, `rule` must be
'IRI_reference' or some special case thereof ('IRI', 'absolute_IRI',
'irelative_ref', 'irelative_part', 'URI_reference', 'URI', 'absolute_URI',
'relative_ref', 'relative_part'). ::

    >>> d = parse('http://tools.ietf.org/html/rfc3986#appendix-A',
    ...           rule='URI')
    >>> assert all([ d['scheme'] == 'http',
    ...              d['authority'] == 'tools.ietf.org',
    ...              d['path'] == '/html/rfc3986',
    ...              d['query'] == None,
    ...              d['fragment'] == 'appendix-A' ])

compose (**parts)
Returns an URI composed_ from named parts.

.. _composed: http://tools.ietf.org/html/rfc3986#section-5.3

resolve (base, uriref, strict=True, return_parts=False)
Resolves_ an URI reference relative to a base URI.

`Test cases <http://tools.ietf.org/html/rfc3986#section-5.4>`_::

    >>> base = resolve.test_cases_base
    >>> for relative, resolved in resolve.test_cases.items():
    ...     assert resolve(base, relative) == resolved

If `return_parts` is True, returns a dict of named parts instead of
a string.

Examples::

    >>> assert resolve('urn:rootless', '../../name') == 'urn:name'
    >>> assert resolve('urn:root/less', '../../name') == 'urn:/name'
    >>> assert resolve('http://a/b', 'http:g') == 'http:g'
    >>> assert resolve('http://a/b', 'http:g', strict=False) == 'http://a/g'

.. _Resolves: http://tools.ietf.org/html/rfc3986#section-5.2

patterns
A dict of regular expressions with useful group names.
Compilable (with regex_ only) without need for any particular compilation
flag.

[bmp_][u]patterns[_no_names]
Alternative versions of patterns.
[u]nicode strings without group names for the re_ module.
BMP only for narrow builds.

get_compiled_pattern (rule, flags=0)
Returns a compiled pattern object for a rule name or template string.

Usage for validation::

    >>> uri = get_compiled_pattern('^%(URI)s$')
    >>> assert uri.match('http://tools.ietf.org/html/rfc3986#appendix-A')
    >>> assert not get_compiled_pattern('^%(relative_ref)s$').match('#f#g')
    >>> from unicodedata import lookup
    >>> smp = 'urn:' + lookup('OLD ITALIC LETTER A')  # U+00010300
    >>> assert not uri.match(smp)
    >>> m = get_compiled_pattern('^%(IRI)s$').match(smp)

On narrow builds, non-BMP characters are (incorrectly) excluded::

    >>> assert NARROW_BUILD == (not m)

For parsing, some subcomponents are captured in named groups (*only if*
regex_ is available, otherwise see `parse`)::

    >>> match = uri.match('http://tools.ietf.org/html/rfc3986#appendix-A')
    >>> d = match.groupdict()
    >>> if REGEX:
    ...     assert all([ d['scheme'] == 'http',
    ...                  d['authority'] == 'tools.ietf.org',
    ...                  d['path'] == '/html/rfc3986',
    ...                  d['query'] == None,
    ...                  d['fragment'] == 'appendix-A' ])

    >>> for r in patterns.keys():
    ...     assert get_compiled_pattern(r)

format_patterns (**names)
Returns a dict of patterns (regular expressions) keyed by
rule names for URIs_ and rule names for IRIs_.

See also the module level dicts of patterns, and `get_compiled_pattern`.

To wrap a rule in a named capture group, pass it as keyword argument:
rule_name='group_name'. By default, the formatted patterns contain no
named groups.

Patterns are `str` instances (be it in python 2.x or 3.x) containing ASCII
characters only.

Caveats:

  - with re_, named capture groups cannot occur on multiple branches of an
    alternation

  - with re_ before python 3.3, ``\u`` and ``\U`` escapes must be
    preprocessed (see `issue3665 <http://bugs.python.org/issue3665>`_)

  - on narrow builds, character ranges beyond BMP are not supported

.. _rule names for URIs: http://tools.ietf.org/html/rfc3986#appendix-A
.. _rule names for IRIs: http://tools.ietf.org/html/rfc3987#section-2.2

Dependencies

Some features require regex_.

This package's docstrings are tested on python 2.6, 2.7, and 3.2 to 3.6.
Note that in python<=3.2, characters beyond the Basic Multilingual Plane are
not supported on narrow builds (see issue12729 <http://bugs.python.org/issue12729>_).

Release notes

version 1.3.8:

fixed deprecated escape sequence

version 1.3.6:

fixed a bug in IPv6 pattern:

assert match('::0:0:0:0:0.0.0.0', 'IPv6address')

version 1.3.4:

allowed for lower case percent encoding

version 1.3.3:

fixed a bug in resolve which left "../" at the beginning of some paths

version 1.3.2:

convenience function match
patterns restricted to the BMP for narrow builds
adapted doctests for python 3.3
compatibility with python 2.6 (thanks to Thijs Janssen)

version 1.3.1:

some re_ compatibility: get_compiled_pattern, parse
dropped regex_ from setup.py requirements

version 1.3.0:

python 3.x compatibility
format_patterns

version 1.2.1:

compose, resolve

.. _re: http://docs.python.org/library/re
.. _regex: http://pypi.python.org/pypi/regex

Support

This is free software. You may show your appreciation with a donation_.

.. _donation: http://danielgerber.net/¤#Thanks-for-python-package-rfc3987

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