Permutation lowercase and uppercase in python

Question

I want this result but not by string ,by input() and Number of characters unknown!

mystring = 'abcd'
for a in (mystring[0].upper(), mystring[0].lower()):
    for b in (mystring[1].upper(), mystring[1].lower()):
        for c in (mystring[2].upper(), mystring[2].lower()):
            for d in (mystring[3].upper(), mystring[3].lower()):
                print(a+b+c+d)

Answer 1

One approach using swapcase and itertools.permutation:

from itertools import product

mystring = 'abcd'
cases = zip(*[mystring, mystring.swapcase()])
for permutation in product(*cases):
    print("".join(permutation))

Output

abcd
abcD
abCd
abCD
aBcd
aBcD
aBCd
aBCD
Abcd
AbcD
AbCd
AbCD
ABcd
ABcD
ABCd
ABCD