Python TypeError: ' Nonetype ' object is not iterable

List (set (map (lambda tp_id:tp_id If not (' # ' in tp_id) and Len (Tp_id.strip (). replace (' \ n ', ')) > 0
else None, open (' Tp_list.txt '). ReadLines ()). Sort ()))

To practice the map, think of a loop as a line of code.

There is a problem with the structure running program: TypeError: ' Nonetype ' object is not iterable.

Find a half-day error (write a line of code at this time is really dead)

Found to be the sort problem, the list's member method sort () Sorts a list (which changes the list) but returns none.

None is non-iterative. So I made such a mistake.

Python TypeError: ' Nonetype ' object is not iterable