Verify is a painless assertion library for Python.

• Project: https://github.com/dgilland/verify
• Documentation: http://verify.readthedocs.org
• PyPI: https://pypi.python.org/pypi/verify/
• TravisCI: https://travis-ci.org/dgilland/verify

Install using pip:

pip install verify

Verify some value using multiple assertions:

from verify import expect, Not, Truthy, Falsy, Less, Greater

expect(5 * 5,
       Truthy(),
       Not(Falsy),
       Greater(15),
       Less(30))

Verify using your own assert functions:

def is_just_right(value):
    assert value == 'just right', 'Not just right!'

# Passes
expect('just right', is_just_right)

# Fails
try:
    expect('too cold', is_just_right)
expect AssertionError:
    raise

NOTE: The assert function should return a truthy value, otherwise, expect will treat the falsy return from the function as an indication that it failed and subsequently raise it's own AssertionError.

Or your own predicate functions:

def is_awesome(value):
    return 'awesome' in value

def is_more_awesome(value):
    return value > 'awesome'

expect('so awesome', is_awesome, is_more_awesome)

Or use chaining syntax:

expect(1).Truthy().Number().NotBoolean().Not(is_awesome)

But you don't have to use expect since the verify assertions can also be used on their own:

import verify

# These would pass.
verify.Truthy(1)
verify.Equal(2, 2)
verify.Greater(3, 2)

# These would fail with an AssertionError
verify.Truthy(0)
verify.Equal(2, 3)
verify.Greater(2, 3)

And if you'd prefer to see assert being used, all verify assertions will return truthy if no AssertionError is raised:

assert Truthy(1)
assert expect(1, Truthy(), Number())

All of the validators in verify are callables that can be used in two contexts:

1. By themselves as in Equal(a, b) which will raise an AssertionError if false.
2. In combination with expect as in expect(a, Equal(b)) which could also raise an AssertionError.

The available validators are:

For more details, please see the full documentation at http://verify.readthedocs.org.