Python 2 will perform floating point division if either the divisor or divident is floating point. Constants are floating point if you include a decimal point. 4 is an int. 4.0 a float. Or you could cast an int variable to float with a float().

I've just refreshed the kata so all Python language version should be enabled ;-)

CW uses 3.4.3 (3.6 hasn't been working for quite a long time already) so that might explain the differences.

yep I tested it and Voile is right, the empty test is the issue.

"""
>>> head_of_list([])

"""

Interestingly enough when I tested this code myself it works in Idle but I'm using 3.6 and codewars isn't. So either testing none is causing errors due to python versioning issues or (more likely) its an issue with how I've written the test cases.

Anyway, the following None test DOES WORK:

>>> head_of_list([]) is None
True

I think it comes from your line after >>> head_of_list([]), which has a completely wrong indentation.

Also, that's not the way for checking if the result is None.

could you show the code? If I can recreate the issue myself, I might be able to figure it out. :)