How to fix TypeError: 'NoneType' object is not iterable in Python?

Question

How can I resolve this problem?

def common_elements(tuple1, tuple2):
    set1 = set(tuple1)
    set2 = set(tuple2)
    lst1 = list(set1.intersection(set2))
    return tuple(lst1.sort()) #TypeError: 'NoneType' object is not iterable

print(common_elements((1, 2, 3, 4), (4, 53, 3, 5, 2, 5, 2, 6, 0)))

Answer 1

list.sort() will sort the list in-place, but the return value is None.

sorted(list) will return a new list object that is sorted.

The correct code should thus be:

def common_elements(tuple1, tuple2):
    set1 = set(tuple1)
    set2 = set(tuple2)
    lst1 = list(set1.intersection(set2))
    return tuple(sorted(lst1))

print(common_elements((1, 2, 3, 4), (4, 53, 3, 5, 2, 5, 2, 6, 0)))

Answer 2

sort() sorts a list in place and returns None . You need to call sort() and then return the same list in two different statements:

lst1.sort()
return tuple(lst1)