function to check if given input is a natural number. with an additional parameter (function) limit of the number can be set

isNaturalNumber.py

def isN(x, func=None):
    try:
        val = int(x)
        return (len(str(val)) is len(str(x))) and \
               (func(val) if callable(func) else True)
    except ValueError:
        return False

print(
    isN(10, (lambda x: -10 <= x <= 10)))
print(
    isN(1.0, (lambda x: -10 <= x <= 10)))
print(
    all(map(lambda x: isN(x), [1, 2, -1, -2, "1", 0, +3, -3])))