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Parsing and validation of URIs (RFC 3896) and IRIs (RFC 3987)

Project description

This module provides regular expressions according to RFC 3986 “Uniform Resource Identifier (URI): Generic Syntax” and RFC 3987 “Internationalized Resource Identifiers (IRIs)”, and utilities for composition and relative resolution of references.

API

patterns

A dict of regular expressions (patterns) keyed by rule names for URIs and rule names for IRIs.

Patterns are str instances (be it in python 2.x or 3.x) containing ASCII characters only. They can be compiled with regex, without need for any particular compilation flag:

>>> import regex
>>> uri = regex.compile('^%s$' % patterns['URI'])
>>> m = uri.match('http://tools.ietf.org/html/rfc3986#appendix-A')
>>> d = m.groupdict()
>>> assert all([ d['scheme'] == 'http',
...              d['authority'] == 'tools.ietf.org',
...              d['path'] == '/html/rfc3986',
...              d['query'] == None,
...              d['fragment'] == 'appendix-A' ])
>>> from unicodedata import lookup
>>> smp = 'urn:' + lookup('OLD ITALIC LETTER A')  # U+00010300
>>> assert not uri.match(smp)
>>> assert regex.match('^%s$' % patterns['IRI'], smp)
>>> assert not regex.match('^%s$' % patterns['relative_ref'], '#f#g')

Alternatively, the standard library re module can be used provided that:

  • \u and \U escapes are preprocessed (see issue3665):

    >>> import re, sys, ast
    >>> re.compile(patterns['ucschar']) #doctest:+IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
      ...
      File "/usr/lib/python2.6/re.py", line 245, in _compile
        raise error, v # invalid expression
    error: bad character range
    >>> tpl = 'u"%s"' if sys.version_info[0] < 3 else '"%s"'
    >>> utext_pattern = ast.literal_eval(tpl % patterns['ucschar'])
    >>> assert re.compile(utext_pattern)
    
  • named capture groups do not occur on multiple branches of an alternation:

    >>> re.compile(patterns['path']) #doctest:+IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
      ...
      File "/usr/lib/python2.6/re.py", line 245, in _compile
        raise error, v # invalid expression
    error: redefinition of group name 'path' as group 2; was group 1
    >>> pat = format_patterns(path='outermost_group_name')['path']
    >>> assert re.compile(pat)
    
format_patterns

Returns a dict of regular expressions keyed by rule name.

By default, the formatted patterns contain no named capture groups. To wrap the pattern of a rule in a named group, pass a keyword argument of the form rule_name=’group_name’. For a useful set of group names, see also patterns.

compose
Returns an URI composed from named parts.
resolve

Resolves an URI reference relative to a base URI.

Test cases:

>>> base = "http://a/b/c/d;p?q"
>>> for relative, resolved in {
...     "g:h"           :  "g:h",
...     "g"             :  "http://a/b/c/g",
...     "./g"           :  "http://a/b/c/g",
...     "g/"            :  "http://a/b/c/g/",
...     "/g"            :  "http://a/g",
...     "//g"           :  "http://g",
...     "?y"            :  "http://a/b/c/d;p?y",
...     "g?y"           :  "http://a/b/c/g?y",
...     "#s"            :  "http://a/b/c/d;p?q#s",
...     "g#s"           :  "http://a/b/c/g#s",
...     "g?y#s"         :  "http://a/b/c/g?y#s",
...     ";x"            :  "http://a/b/c/;x",
...     "g;x"           :  "http://a/b/c/g;x",
...     "g;x?y#s"       :  "http://a/b/c/g;x?y#s",
...     ""              :  "http://a/b/c/d;p?q",
...     "."             :  "http://a/b/c/",
...     "./"            :  "http://a/b/c/",
...     ".."            :  "http://a/b/",
...     "../"           :  "http://a/b/",
...     "../g"          :  "http://a/b/g",
...     "../.."         :  "http://a/",
...     "../../"        :  "http://a/",
...     "../../g"       :  "http://a/g",
...     "../../../g"    :  "http://a/g",
...     "../../../../g" :  "http://a/g",
...     "/./g"          :  "http://a/g",
...     "/../g"         :  "http://a/g",
...     "g."            :  "http://a/b/c/g.",
...     ".g"            :  "http://a/b/c/.g",
...     "g.."           :  "http://a/b/c/g..",
...     "..g"           :  "http://a/b/c/..g",
...     "./../g"        :  "http://a/b/g",
...     "./g/."         :  "http://a/b/c/g/",
...     "g/./h"         :  "http://a/b/c/g/h",
...     "g/../h"        :  "http://a/b/c/h",
...     "g;x=1/./y"     :  "http://a/b/c/g;x=1/y",
...     "g;x=1/../y"    :  "http://a/b/c/y",
...     }.items():
...     assert resolve(base, relative) == resolved

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

What’s new

version 1.3.0:

  • python 3.x compatibility
  • format_patterns

version 1.2.1:

  • compose, resolve

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