tmf16

# ng
>>> arr = [1, 2, 3, 4, 5]
>>> ', '.join(arr)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: sequence item 0: expected string, int found

# ok
>>> arr = [1, 2, 3, 4, 5]
>>> ', '.join(map(str, arr))