Reduce Fractions Function Python

A function that reduces/simplifies fractions using the Euclidean Algorithm, in Python.


def reducefract(n, d):
    '''Reduces fractions. n is the numerator and d the denominator.'''
    def gcd(n, d):
        while d != 0:
            t = d
            d = n%d
            n = t
        return n
    assert d!=0, "integer division by zero"
    assert isinstance(d, int), "must be int"
    assert isinstance(n, int), "must be int"
    greatest=gcd(n,d)
    n/=greatest
    d/=greatest
    return n, d