def is_permutation(a, b):
    """Returns True is the digits of b are a permutation of the digits of a"""
    a, b = list(str(a)), list(str(b))
    if len(a) != len(b):
        return False
    else:
        for item in a:
            if item not in b:
                return False
            else:
                b.remove(item)
        return True