nlesc-nano / assertionlib

A package for performing assertions and providing informative exception messages.

AssertionLib

A package for performing assertions and providing informative exception messages.

Installation

• PyPi: pip install AssertionLib
• GitHub: pip install git+https://github.com/nlesc-nano/AssertionLib

Usage

A comprehensive overview of all available assertion methods is provided in the documentation. A few examples of some basic assertion:

>>> import numpy as np
>>> from assertionlib import assertion

# Assert the output of specific callables
>>> assertion.eq(5, 5)  # 5 == 5
>>> assertion.lt(5, 6)  # 5 < 6
>>> assertion.gt(6, 5)  # 5 > 6
>>> assertion.isinstance(5, int)
>>> assertion.hasattr(5, '__init__')
>>> assertion.any([False, False, True])
>>> assertion.isfinite(1.0)

# Simply assert a value
>>> assertion(5 == 5)
>>> assertion(isinstance(5, int))

# Apply post-processing before conducting the assertion
>>> ar_large = np.ones(10)
>>> ar_small = np.zeros(10)
>>> assertion.gt(ar_large, ar_small, post_process=np.all)  # all(ar_large > ar_small)

# Perform an assertion which will raise an AssertionError
>>> assertion.eq(5, 6, message='Fancy custom error message')  # 5 == 6
Traceback (most recent call last):
  ...
AssertionError: output = eq(a, b); assert output

exception: AssertionError = AssertionError('Fancy custom error message')

output: bool = False
a: int = 5
b: int = 6

A few examples of AssertionErrors raised due to incorrect method signatures:

>>> from assertionlib import assertion

>>> assertion.len(5)
Traceback (most recent call last):
  ...
AssertionError: output = len(obj); assert output

exception: TypeError = TypeError("object of type 'int' has no len()")

output: NoneType = None
obj: int = 5

>>> from assertionlib import assertion

>>> assertion.eq(5, 5, 5, 5)
Traceback (most recent call last):
  ...
AssertionError: output = eq(a, b, _a, _b); assert output

exception: TypeError = TypeError('eq expected 2 arguments, got 4')

output: NoneType = None
a: int = 5
b: int = 5
_a: int = 5
_b: int = 5

A demonstration of the exception parameter. Providing an exception type will assert that the provided exception is raised during/before the assertion process:

>>> from assertionlib import assertion

>>> len(5)
Traceback (most recent call last):
  ...
TypeError: object of type 'int' has no len()

>>> from assertionlib import assertion

>>> assertion.len(5, exception=TypeError)  # i.e. len(5) should raise a TypeError
>>> assertion.len([5], exception=TypeError)
Traceback (most recent call last):
  ...
AssertionError: output = len(obj); assert output

exception: AssertionError = AssertionError("Failed to raise 'TypeError'")

output: int = 1
obj: list = [5]

Lastly, the output of custom callables can be asserted in one of the following two ways, supplying the callable to AssertionManager.assert() or creating a custom assertion method and adding it to an instance with AssertionManager.add_to_instance():

>>> from assertionlib import assertion

>>> def my_fancy_func(a: object) -> bool:
...     return False

# Approach #1, supply to-be asserted callable to assertion.assert_()
>>> assertion.assert_(my_fancy_func, 5)
Traceback (most recent call last):
  ...
AssertionError: output = my_fancy_func(a); assert output

exception: AssertionError = AssertionError(None)

output: bool = False
a: int = 5

>>> from assertionlib import assertion

# Approach #2, permanantly add a new bound method using assertion.add_to_instance()
>>> assertion.add_to_instance(my_fancy_func)
>>> assertion.my_fancy_func(5)
Traceback (most recent call last):
  ...
AssertionError: output = my_fancy_func(a); assert output

exception: AssertionError = AssertionError(None)

output: bool = False
a: int = 5

assertionlib's Issues

Enable `pandas` and `numpy` as testing requirements for Python 3.9

pandas and numpy are currently disabled as testing requirements for Python 3.9 as their installation simply takes too long, especially pandas.
Enable them once Python 3.9 has been released (see PEP 596) and wheels are available for aforementioned packages.

README.rst not included in PyPI

This README is loaded in the __init__.py. However, as this README is not included in the PyPI distribution, this causes errors when trying to import the package:

failing sanity check for 'AssertionLib' extension: command "python -c "import assertionlib"" failed; output:
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/lib/python3.9/site-packages/assertionlib/__init__.py", line 14, in <module>
    __doc__ = load_readme(_README, encoding='utf-8')
  File "/lib/python3.9/site-packages/assertionlib/functions.py", line 467, in load_readme
    with open(readme, **kwargs) as f:
FileNotFoundError: [Errno 2] No such file or directory: '/lib/python3.9/site-packages/assertionlib/README.rst',