import itertools
ls = [['a', 'b', 'c'], ['d', 'e', 'f'], ['g', 'h', 'i']]
res = []
for i in itertools.product(*ls):
res.append(''.join(i))
print(res)

import itertools
ls = [['a', 'b', 'c'], ['d', 'e', 'f'], ['g', 'h', 'i']]
res = []
for i in itertools.product(*ls):
res.append(''.join(i))
print(res)