modulus.py

# It frustrates you more than you'd like to admit that the modulus operator in Python can be applied to non-integer values. When you write code, you expect the result of the modulus operator to always be an integer, but thanks to Python this isn't always the case.

# To fix this, you've decided to write your own modulus operator as a function. Your task is to implement a function that, given a number n, returns -1 if this number is not an integer and n % 2 otherwise. It is guaranteed that if the number represents an integer, it will be written without a decimal point.
def modulus(n):
    if float(n).is_integer():
        return n % 2
    else:
        return -1