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+:mod:`packaging.version` --- Version number classes
+===================================================
+
+.. module:: packaging.version
+   :synopsis: Classes that represent project version numbers.
+
+
+This module contains classes and functions useful to deal with version numbers.
+It's an implementation of version specifiers `as defined in PEP 345
+<http://www.python.org/dev/peps/pep-0345/#version-specifiers>`_.
+
+
+Version numbers
+---------------
+
+.. class:: NormalizedVersion(self, s, error_on_huge_major_num=True)
+
+   A specific version of a distribution, as described in PEP 345.  *s* is a
+   string object containing the version number (for example ``'1.2b1'``),
+   *error_on_huge_major_num* a boolean specifying whether to consider an
+   apparent use of a year or full date as the major version number an error.
+
+   The rationale for the second argument is that there were projects using years
+   or full dates as version numbers, which could cause problems with some
+   packaging systems sorting.
+
+   Instances of this class can be compared and sorted::
+
+      >>> NormalizedVersion('1.2b1') < NormalizedVersion('1.2')
+      True
+
+   :class:`NormalizedVersion` is used internally by :class:`VersionPredicate` to
+   do its work.
+
+
+.. class:: IrrationalVersionError
+
+   Exception raised when an invalid string is given to
+   :class:`NormalizedVersion`.
+
+      >>> NormalizedVersion("irrational_version_number")
+      ...
+      IrrationalVersionError: irrational_version_number
+
+
+.. function:: suggest_normalized_version(s)
+
+   Before standardization in PEP 386, various schemes were in use.  Packaging
+   provides a function to try to convert any string to a valid, normalized
+   version::
+
+      >>> suggest_normalized_version('2.1-rc1')
+      2.1c1
+
+
+   If :func:`suggest_normalized_version` can't make sense of the given string,
+   it will return ``None``::
+
+      >>> print(suggest_normalized_version('not a version'))
+      None
+
+
+Version predicates
+------------------
+
+.. class:: VersionPredicate(predicate)
+
+   This class deals with the parsing of field values like
+   ``ProjectName (>=version)``.
+
+   .. method:: match(version)
+
+      Test if a version number matches the predicate:
+
+         >>> version = VersionPredicate("ProjectName (<1.2, >1.0)")
+         >>> version.match("1.2.1")
+         False
+         >>> version.match("1.1.1")
+         True
+
+
+Validation helpers
+------------------
+
+If you want to use :term:`LBYL`-style checks instead of instantiating the
+classes and catching :class:`IrrationalVersionError` and :class:`ValueError`,
+you can use these functions:
+
+.. function:: is_valid_version(predicate)
+
+   Check whether the given string is a valid version number.  Example of valid
+   strings: ``'1.2'``,  ``'4.2.0.dev4'``, ``'2.5.4.post2'``.
+
+
+.. function:: is_valid_versions(predicate)
+
+   Check whether the given string is a valid value for specifying multiple
+   versions, such as in the Requires-Python field.  Example: ``'2.7, >=3.2'``.
+
+
+.. function:: is_valid_predicate(predicate)
+
+   Check whether the given string is a valid version predicate.  Examples:
+   ``'some.project == 4.5, <= 4.7'``, ``'speciallib (> 1.0, != 1.4.2, < 2.0)'``.