def common_divisors_generator(n, m):

    # Init code
    factors_n = [i for i in range(1, n + 1) if n%i == 0]
    factors_m = [i for i in range(1, m + 1) if m%i == 0]

    # Recursive code
    for fn in factors_n:
        for fm in factors_m:
            if fn == fm:
                yield fn

# The next line is fast because no code is executed yet
cdg = common_divisors_generator(1537745, 373625435)
# Next line is slow because init code is executed on first iteration call
for g in cdg:
    print(g)

class CommonDivisorsIterator(object):

    def __init__(self, n, m):
        # Init code
        self.factors_n = [i for i in range(1, n + 1) if n%i == 0]
        self.factors_m = [i for i in range(1, m + 1) if m%i == 0]

    def __iter__(self):
        return self

    def __next__(self):
        # Some Pythonic implementation of the recursive code above
        # ...
        return next_common_divisor