def swap(my_string):

    # initialise result to ""
    result = ""

    # go through the characters of the string
    for i in range(len(my_string)):
        current_char = my_string[i]

        # if current character is uppercase, swap it to lower
        if current_char.isupper():
            result = result + current_char.lower()
        # if current character is lowercase, swap it to upper
        elif current_char.islower():
            result = result + current_char.upper()
        else:
            result = result + current_char

    return result

# lower(), upper(), isupper(), islower()

my_string = "Henry"
print(swap(my_string))
assert swap(my_string) == "hENRY"