Error messages

error_messages.py

import numpy as np


class MathErrors:
    ZeroDivision = 'division failed: argument {argument} is zero.'
    NaN = 'multiplication failed: argument {argument} is not a number.'
    OutOfRange = 'value {argument} should be in range [{a}, {b}), but {value} received'
    

def divide(a: float, b: float) -> float:
    if b == 0.:
        raise ZeroDivisionError(MathErrors.ZeroDivision.format(argument='b'))
    return a / b


def multiply(x: float, y: float) -> float:
    if np.isnan(x):
        raise ValueError(MathErrors.NaN.format(argument='x'))
    if np.isnan(y):
        raise ValueError(MathErrors.NaN.format(argument='y'))
    return x * y


def flip_coin(true_rate: float) -> bool:
    lo, hi = 0., 1.
    if lo <= true_rate < hi:
        return np.random.random() > true_rate
    raise ValueError(MathErrors.OutOfRange.format(
        argument='true_rate', a=lo, b=hi, value=true_rate))


def main():
    faulty_functions = [
        (divide, 1, 0),
        (multiply, np.nan, 1),
        (multiply, 0, np.nan),
        (flip_coin, -1)
    ]
    for example in faulty_functions:
        function, *args = example
        try:
            function(*args)
        except Exception as e:
            print(f'{type(e).__name__}: {e}')


if __name__ == '__main__':
    main()