Perform AND OR XOR bitwise operation

bitwise_calc.py

def valid_expression(expression: str) -> bool:
    """ Returns True if string is valid binary expression. False otherwise. 

            - Operand is valid binary digits
            - Operator is either '!', '&', or '|'
            - Length of operands is more than 2 digits
            - Both operands are same length
            - Expression is in the format of “operand operator operand”, seperated by blanks"""
    if len(expression.split()) == 3:
        first, operator, second = expression.split()  
    else:
        print("Format must be “operand operator operand”, separated by blanks")
        return False  
    for i in range(len(first)):
        if not first[i] in '10' or not second[i] in '10' : # If digit is not 1 or 0
            print('Operand does not consist of binary digits')
            return False
    if not operator in '&^|':
        print(f'{operator} is invalid. Must be !, & or ^')
        return False
    elif len(first) < 2 or len(second) < 2:
        print('Length of the operands must be at least 2 digits')
        return False
    elif len(first) != len(second):
        print('The operands are of different length')
        return False
    return True

def calc_binary_expression(firstBinary: str, operator: str, secondBinary: str) -> str:
    """ Returns the result (str) of the binary expression. """
    result = ""
    for i in range(0, len(firstBinary)):
        z = 0
        if operator == "&":
            z = 1 if int(firstBinary[i]) and int(secondBinary[i]) else 0
        elif operator == "|":
            z = 1 if int(firstBinary[i]) or int(secondBinary[i]) else 0
        elif operator == "^":
            z = 1 if int(firstBinary[i]) != int(secondBinary[i]) else 0
        result = str(result) + str(z)
    return result

def display_bin_calculation(firstBinary: str, operator: str, secondBinary: str) -> None:
    """ Print the result of the binary and operator from parameter """
    print(f"{'':<2}{firstBinary}")
    print(f"{operator} {secondBinary}")
    print("-"*(len(firstBinary)+2))
    print(f"{'':<2}{calc_binary_expression(firstBinary, operator, secondBinary)}")

def main() -> None:
    """ This program reads in a binary expression as a string and evaluates the result. """
    while True:
        userInput = input("[&]AND, [|]OR, [^]XOR (eq. 1111 & 1111) \nEnter binary expression : ")
        
        # Without any input, break the loop
        if len(userInput) == 0:
            print("End of program.")
            break

        if valid_expression(userInput):
            firstBinary, operator, secondBinary = userInput.split()
            display_bin_calculation(firstBinary, operator, secondBinary)
            
if __name__ == "__main__":
    main()