python 3.x - how to define decryption of caeser cipher -

ok missed class , trying work did in there. 1 of problems fixing caeser cipher. believe have fixed except last part of course part i'm stuck on. have.

#change t lowercase in plaintext #add : end of if statement       def encrypt(plaintext, alphabet, key):                plaintext = plaintext.lower()         ciphertext = ""         ch in plaintext:             idx = alphabet.find(ch)             if idx >= 0 , idx <= 25:                 ciphertext = ciphertext + key[idx]             else:                 ciphertext = ciphertext + ch                 #add return ciphertext         return ciphertext #add def decrypt line def decrypt(ciphertext, alphabet, key):         plaintext = ""         ch in ciphertext:             idx = key.find(ch)             #add , idx <= 25 if statement             if idx >= 0 , idx <= 25:                 plaintext = plaintext + alphabet[idx]             else:                 plaintext = plaintext + ch         return plaintext #got rid of def main #have mycipher = encrypt # define both mycipher , plain encrypt , decrypt alphabet = "abcdefghijklmnopqrstuvwxyz" key = "nopqrstuvwxyzabcdefghijklm" plaintext = input("enter text want encrypt: " ) mycipher = encrypt(plaintext, alphabet, key) myplain = decrypt(ciphertext,alphabet, key)   print(mycipher) print("checking if decryption works: ") print(myplain) 

when run code says ciphertext not defined in

myplain = decrypt(ciphertext,alphabet, key) 

i have tried few different options seem going further fixing have now. way can define ciphertext in line or have redo line , change else?

this error when tried change ciphertext laloldublin suggested

 traceback (most recent call last):   file "c:\users\david\downloads\caeser (2).py", line 32, in <module>     myplain = decrypt(mycipher ,alphabet, key)   file "c:\users\david\downloads\caeser (2).py", line 21, in decrypt     plaintext = plaintext + alphabet[idx] unboundlocalerror: local variable 'plaintext' referenced before assignment 

you can't use ciphertext it's local variable within function...

mycipher = encrypt(plaintext, alphabet, key) myplain = decrypt(mycipher ,alphabet, key)