Requirements

Parse a given requirements line for specifying dependencies of a Python project, using the specification of dependency specifiers, 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

Changed in version 23.2: When a requirement is specified with a URL, the Requirement class used to check the URL and reject values containing invalid scheme and netloc combinations. This is no longer performed since the specification does not have such rules, and the check incorrectly disallows valid requirement strings from being parsed.

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 the specification.

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 the specification.