Python 3 – there shall be just int

Trying to contribute to the Flask plugin flask-login I just added these lines:

if isinstance(duration, (int, long)):
    duration = timedelta(seconds=duration)

Looking quite plausible, isn’t it? But lo and behold: it doesn’t work under Python 3.x. Dang!

The reason: Python 2 has two integer types: int and long. In Python 3 there is only int, which makes it necessary to distinguish between these two major versions. I’ve found a nice page which deals with this issue. Here is what You must do to make it work in both Python 2 and 3:

import sys
if sys.version_info < (3,):
    integer_types = (int, long,)
    integer_types = (int,)

isinstance(1, integer_types)