Requirements#

Parse a given requirements line for specifying dependencies of a Python project, using PEP 508 which defines the scheme that has been implemented by this module.

Usage#

>>> from packaging.requirements import Requirement
>>> simple_req = Requirement("name")
>>> simple_req
<Requirement('name')>
>>> simple_req.name
'name'
>>> simple_req.url is None
True
>>> simple_req.extras
set()
>>> simple_req.specifier
<SpecifierSet('')>
>>> simple_req.marker is None
True
>>> # Requirements can be specified with extras, specifiers and markers
>>> req = Requirement('name[foo]>=2,<3; python_version>"2.0"')
>>> req.name
'name'
>>> req.extras
{'foo'}
>>> req.specifier
<SpecifierSet('<3,>=2')>
>>> req.marker
<Marker('python_version > "2.0"')>
>>> # Requirements can also be specified with a URL, but may not specify
>>> # a version.
>>> url_req = Requirement('name @ https://github.com/pypa ;os_name=="a"')
>>> url_req.name
'name'
>>> url_req.url
'https://github.com/pypa'
>>> url_req.extras
set()
>>> url_req.marker
<Marker('os_name == "a"')>
>>> # You can do simple comparisons between requirement objects:
>>> Requirement("packaging") == Requirement("packaging")
True
>>> # You can also perform simple comparisons between sets of requirements:
>>> requirements1 = {Requirement("packaging"), Requirement("pip")}
>>> requirements2 = {Requirement("pip"), Requirement("packaging")}
>>> requirements1 == requirements2
True

Reference#

class packaging.requirements.Requirement(requirement)#

This class abstracts handling the details of a requirement for a project. Each requirement will be parsed according to PEP 508.

Parameters

requirement (str) – The string representation of a requirement.

Raises

InvalidRequirement – If the given requirement is not parseable, then this exception will be raised.

name#

The name of the requirement.

url#

The URL, if any where to download the requirement from. Can be None.

extras#

A set of extras that the requirement specifies.

specifier#

A SpecifierSet of the version specified by the requirement.

marker#

A Marker of the marker for the requirement. Can be None.

exception packaging.requirements.InvalidRequirement#

Raised when attempting to create a Requirement with a string that does not conform to PEP 508.