[azakai]

Correct, that's a python 2/3 difference. But both 2 and 2 have arbitrary precision integers AFAIK, try this code

    x = 1
    for i in range(100):
        x = x*2
        print(i, x)

[e12e]

Indeed. Just to verify that it's not just a difference in (string)representation, something like:

    print(9**32-(9**32-5))

Also works (brython returns 0, python2&3 return 5)