проблемы с отладкой pycharm

Используя python:

#!/usr/bin/env python2
import random, string 
def rand_gen(number_of_words, length):
    for i in range(number_of_words):
        print ''.join(random.choice(string.ascii_lowercase + string.ascii_uppercase) for _ in range(length))
    return

Пример:

rand_gen(5, 3)
PDI
qKQ
Dvu
kwr
wDz

rand_gen(2, 5)
GLKXr
uOaHj