Smart atbash coding in Python

atbash.py

def swap(char):
    return chr(swap_ascii(ord(char)))
def swap_ascii(code):
    if code>=65 and code<=90:
        return 155-code
        # 90 - (code-65) = 90+65-code = 115-code
    elif code>=97 and code<=122:
        return 219-code
        # similarly from 112-(code-97)
    return code

def atbash(string):
    return "".join(map(swap, string))

while True:
    print(atbash(input()))