This small python library provides a few tools to handle SemVer in Python. It follows strictly the 2.0.0 version of the SemVer scheme. Latest Version Supported Python versions Wheel status License

Getting started

Install the package from PyPI, using pip:

pip install semantic_version

Or from GitHub:

$ git clone git://

Import it in your code:

import semantic_version

This module provides two classes to handle semantic versions:

  • Version represents a version number (0.1.1-alpha+build.2012-05-15)
  • Spec represents a requirement specification (>=0.1.1,<0.3.0)


Defining a Version is quite simple:

>>> import semantic_version
>>> v = semantic_version.Version('0.1.1')
>>> v.major
>>> v.minor
>>> v.patch
>>> v.prerelease
>>> list(v)
[0, 1, 1, [], []]

If the provided version string is invalid, a ValueError will be raised:

>>> semantic_version.Version('0.1')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/rbarrois/dev/semantic_version/src/semantic_version/", line 64, in __init__
    major, minor, patch, prerelease, build = self.parse(version_string, partial)
  File "/Users/rbarrois/dev/semantic_version/src/semantic_version/", line 86, in parse
    raise ValueError('Invalid version string: %r' % version_string)
ValueError: Invalid version string: '0.1'

In order to define “relaxed” version strings, you must pass in partial=True:

>>> v = semantic_version.Version('0.1', partial=True)
>>> list(v)
[0, 1, None, None, None]

Obviously, Versions can be compared:

>>> semantic_version.Version('0.1.1') < semantic_version.Version('0.1.2')
>>> semantic_version.Version('0.1.1') > semantic_version.Version('0.1.1-alpha')
>>> semantic_version.Version('0.1.1') <= semantic_version.Version('0.1.1-alpha')

You can also get a new version that represents a bump in one of the version levels:

>>> v = semantic_version.Version('0.1.1+build')
>>> new_v = v.next_major()
>>> str(new_v)
>>> v = semantic_version.Version('1.1.1+build')
>>> new_v = v.next_minor()
>>> str(new_v)
>>> v = semantic_version.Version('1.1.1+build')
>>> new_v = v.next_patch()
>>> str(new_v)

It is also possible to check whether a given string is a proper semantic version string:

>>> semantic_version.validate('0.1.3')
>>> semantic_version.validate('0a2')

Requirement specification

The Spec object describes a range of accepted versions:

>>> s = Spec('>=0.1.1')  # At least 0.1.1
>>> s.match(Version('0.1.1'))
>>> s.match(Version('0.1.1-alpha1'))  # pre-release satisfy version spec
>>> s.match(Version('0.1.0'))

Simpler test syntax is also available using the in keyword:

>>> s = Spec('==0.1.1')
>>> Version('0.1.1-alpha1') in s
>>> Version('0.1.2') in s

Combining specifications can be expressed in two ways:

  • Components separated by commas in a single string:

    >>> Spec('>=0.1.1,<0.3.0')
  • Components given as different arguments:

    >>> Spec('>=0.1.1', '<0.3.0')
  • A mix of both versions:

    >>> Spec('>=0.1.1', '!=0.2.4-alpha,<0.3.0')

Using a specification

The Spec.filter() method filters an iterable of Version:

>>> s = Spec('>=0.1.0,<0.4.0')
>>> versions = (Version('0.%d.0' % i) for i in range(6))
>>> for v in s.filter(versions):
...     print v

It is also possible to select the ‘best’ version from such iterables:

>>> s = Spec('>=0.1.0,<0.4.0')
>>> versions = (Version('0.%d.0' % i) for i in range(6))

Coercing an arbitrary version string

Some user-supplied input might not match the semantic version scheme. For such cases, the Version.coerce() method will try to convert any version-like string into a valid semver version:

>>> Version.coerce('0')
>>> Version.coerce('')
>>> Version.coerce('0.1.2a3')

Including pre-release identifiers in specifications

When testing a Version against a Spec, comparisons are only performed for components defined in the Spec; thus, a pre-release version (1.0.0-alpha), while not strictly equal to the non pre-release version (1.0.0), satisfies the ==1.0.0 Spec.

Pre-release identifiers will only be compared if included in the Spec definition or (for the empty pre-release number) if a single dash is appended (1.0.0-):

>>> Version('0.1.0-alpha') in Spec('>=0.1.0')  # No pre-release identifier
>>> Version('0.1.0-alpha') in Spec('>=0.1.0-')  # Include pre-release in checks

Including build metadata in specifications

Build metadata has no ordering; thus, the only meaningful comparison including build metadata is equality.

>>> Version('1.0.0+build2') in Spec('<=1.0.0')   # Build metadata ignored
>>> Version('1.0.0+build2') in Spec('==1.0.0+build2')  # Include build in checks

Using with Django

The semantic_version.django_fields module provides django fields to store Version or Spec objects.

More documentation is available in the Interaction with Django section.


In order to contribute to the source code:

When submitting patches or pull requests, you should respect the following rules:

  • Coding conventions are based on PEP 8
  • The whole test suite must pass after adding the changes
  • The test coverage for a new feature must be 100%
  • New features and methods should be documented in the Reference section and included in the ChangeLog
  • Include your name in the Contributors section


All files should contain the following header:

# -*- encoding: utf-8 -*-
# Copyright (c) The python-semanticversion project

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