anything

Defines the Anything and Something constants.

Anything compares true with any other object:

>>> Anything == 42
True
>>> 'hello' == Anything
True

You can use it to check that specific values in a data structure have a value, but it doesn't matter what they are, for example in a unit test:

>>> [1, 2, 3] == [1, Anything, 3]
True
>>> {'x': 10, 'y': -3} == {'x': 10, 'y': Anything}
True
>>> {'x': 10} == {'x': 10, 'y': Anything}
False

Inequality behaves consistently with equality:

>>> 'hello' != Anything
False

Even None is considered equal to Anything:

>>> Anything == None
True

If you want to make sure that a value is not None, use Something instead:

>>> Something == None
False
>>> Something == 1
True
>>> 1 == Something
True
>>> Something != None
True
>>> Something != 'foo'
False

Something only checks for None specifically, i.e. it does not accept any falsy value:

>>> Something == False
True
>>> Something != False
False

Equality between the two constants works as you probably expect:

>>> Anything == Anything
True
>>> Something == Something
True
>>> Anything == Something
True
>>> Something == Anything
True

Usage in Tests

Example: Creating a user and making sure its data is returned. As the generated ID can be anything, we can't check it's value, but this makes sure it is returned:

import unittest

class MyTest(unittest.TestCase):
    def test_create_user(self):
        data = create_user(name='Mary')
        self.assertEqual({
            'name': 'Mary',
            'id': Anything
        }, data)