Storing data/output from a loop

[ichabod801]

The problem is line 14. The append method modifies the list in place, so you don't need to assign the result to anything. In fact, the result is None. There error is because of that None. The join method needs a list or other sequence/iterable. None is none of those things, so you get an error.

Note that naming your list 'list' is a bad idea. The name 'list' is already used in Python, so if you use it for one of your variables, you can no longer access the built-in list function.

To fix it, rename your list 'strays', and remove the assignment so it's just:

strays.append(countn)