New Project: verify

I've started a new Python project: verify

Verify is billed as

A painless assertion and validation library for Python

Why make this when similar libraries already exist? Simply, I wanted a library with the following features:

  • All objects raise an AssertionError when invalid.
  • Ability to easily apply multiple assertions to a single value either via method chaining or passing multiple arguments to an assertion runner function.
  • Simple callables as assertions.
  • Support for using external predicate functions for validation.

Current Release

As of this writing, the latest version of verify is v0.5.0. It has 70 assertion methods and 100% test coverage.

Sample Usage

Using verify is simple:

import verify as v

# These will pass.
v.expect(5 * 5, v.Truthy(), v.Greater(15), v.Less(30))
v.Equal(2, 2)
v.Greater(3, 2)

# These will fail with an AssertionError
v.Equal(2, 3)
v.Greater(2, 3)

# Using custom assert functions
def is_just_right(value):
    assert value == 'just right', 'Not just right!'
    return True

# Passes
expect('just right', is_just_right)

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

# Using custom 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)

Looking Ahead

Active development is underway with the goal of releasing v1.0.0 soon to lock in a stable API. You can track or contribute to verify on Github.


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