import itertools

for letter1, letter2, letter3 in itertools.product(['a', 'b', 'c', 'd', 'e'], repeat=3):
    print(letter1, letter2, letter3)

for letter1 in ['a', 'b', 'c', 'd', 'e']:
    for letter2 in ['a', 'b', 'c', 'd', 'e']:
        for letter3 in ['a', 'b', 'c', 'd', 'e']:
            print(letter1, letter2, letter3)