# Product(A, B) returns the same as ((x,y) for x in A for y in B).
# Product(A, repeat=4) means the same as product(A, A, A, A).
product('ABCD', repeat=2)

permutations('ABCD', 2)
combinations('ABCD', 2)
combinations_with_replacement('ABCD', 2)

# Excel
# PERMUT(n,r)
# COMBN(n,r)
# PERMUTATIONA(n,r)
# COMBINA(n,r)