Yes, in theory this is a problem in lots of languages which are weakly typed. There are lots of ways of handling this, some generic and some language specific.

In python I would suggest wrapping your call in a try / expect block or using "isinstance()".

If you are using a publicly available library or popular piece of code that can return None or an Integer, I would argue that piece of code was written incorrectly. Newbie python users might do this, but I think experienced python devs would see the problem.

Finally, some documentation or justification for the reasoning behind this decision at the top of the function or on a web page somewhere would help as well.

As with most powerful , full featured languages it is pretty easy to shoot yourself in the foot if you are not careful, I don't think this is a python specific problem...