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Parsing and validation of URIs (RFC 3986) and IRIs (RFC 3987)

Project description

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.

Tested on python 2.7, 3.2 and 3.3. Some features require regex_.

Note for python<=3.2: characters beyond the Basic Multilingual Plane are not
supported on narrow builds (see `issue12729
<http://bugs.python.org/issue12729>`_).


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 (incorreclty) 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



What's new
----------

version 1.3.4:

- allowed for lower case percent encoding

version 1.3.3:

- fixed a bug in `resolve` which left "../" at the begining 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

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