Transposition Cipher Issues

[beginner_geek07]

I am recently new to python and I have been given the task to create a function that uses transposition cipher to encrypt and decrypt a user-input message with a user-input key. However I am stuck on what to do next. I have to use my swap() function inside the transposition cipher and I can only call len(), ord(), and range(). I would really appreciate if someone could show me how to this so that I could do the decryption part myself.

def swap(x, i, j):
    i, j = sorted((i, j))
    if i and j in range(len(x)):
        return x[:i] + x[j] + x[i+1:j] + x[i] + x[j+1:]
    else:
        return None   
plaintext =''
keyword = ''

def swap_encrypt(plaintext, keyword):
    alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    translated_message = ""
    keyword_index = 0
    keyword_index = keyword_index % len(keyword)
    i = swap(keyword_index)

    for character in plaintext:
        if character in alphabet:

If the message is ‘SLOTH POWER’, and the keyword is ‘TOP’, then the output should be something like: ‘RLOTPOHWES’

I just need help on the encryption process.