perofrming caesarcipher for a string using shift

Question

from string import ascii_lowercase as alphabet1
from string import ascii_uppercase as alphabet2

import letter as letter



def cipher(user_input, shift):
    cipher1 = {char: alphabet1[(i + shift) % 26] for i, char in enumerate(alphabet1)}
    cipher2 = {char: alphabet2[(i + shift) % 26] for i, char in enumerate(alphabet2)}
    
    caesar_cipher = ""
    
    for letter in user_input:
        caesar_cipher += cipher1.get(letter, letter)
    else:
        caesar_cipher += cipher2.get(letter, letter)
    return caesar_cipher


if __name__ == "__main__":
    
    user_input = input("Enter the String: ")
    
    shift = int(input("Enter shift: "))
    
    print("Caesar Cipher: " + cipher(user_input, shift))

I am performing Caeser cipher for both upper case and lower case characters. But the result is not correct. cipher1 is for lowercase and cipher 2 is for upper case. I have defined it in a function. And called it in main method the result obtained for lower case is:

Enter the String: abc
Enter shift: 2
Caesar Cipher: cdec

it should be cde

The result obtained for upper case is:

Enter the String: ABC
Enter shift: 2
Caesar Cipher: ABCE

It should be CDE

`...the result is not correct.`. How is it incorrect? What did you use for input, what was the output? What did you expect it to be? Do you suspect a particular part of the code? — wwii, Dec 07 '22 at 04:19
[How to step through Python code to help debug issues?](https://stackoverflow.com/questions/4929251/how-to-step-through-python-code-to-help-debug-issues) If you are using an IDE **now** is a good time to learn its debugging features Or the built-in [Python debugger](https://docs.python.org/3/library/pdb.html). Printing *stuff* at strategic points in your program can help you trace what is or isn't happening. [What is a debugger and how can it help me diagnose problems?](https://stackoverflow.com/questions/25385173/what-is-a-debugger-and-how-can-it-help-me-diagnose-problems). — wwii, Dec 07 '22 at 04:20
[collections.deque](https://docs.python.org/3/library/collections.html#collections.deque) has a rotate method which might be usefull. — wwii, Dec 07 '22 at 04:24

wwii · Accepted Answer · 2022-12-07T04:51:12.050

0

Check whether each letter is upper or lower case then use the corresponding cipher.

    ...
    
    for letter in user_input:
        cipher = cipher1 if letter in cipher1 else cipher2
        print(cipher[letter])

c
D
e

When the iterator is exhausted, the suite in the else clause, if present, is executed, and the loop terminates.

Your else clause was always executing.

For loop

edited Dec 07 '22 at 04:51

answered Dec 07 '22 at 04:42

wwii

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I need to take input from the user. Can you modify the above code only @wwii – Jyoti Dec 07 '22 at 04:46

score 0 · Answer 2 · edited Dec 09 '22 at 16:28

from string import ascii_lowercase as alphabet1
from string import ascii_uppercase as alphabet2

import letter as letter



def cipher(user_input, shift):
    cipher1 = {char: alphabet1[(i + shift) % 26] for i, char in enumerate(alphabet1)}
    cipher2 = {char: alphabet2[(i + shift) % 26] for i, char in enumerate(alphabet2)}
    
    caesar_cipher = ""
    
    for letter in user_input:
        caesar_cipher += cipher1.get(letter, letter)
    else:
        caesar_cipher += cipher2.get(letter, letter)
    return caesar_cipher


if __name__ == "__main__":
    
    user_input = input("Enter the String: ")
    
    shift = int(input("Enter shift: "))
    
    print("Caesar Cipher: " + cipher(user_input, shift))

perofrming caesarcipher for a string using shift

2 Answers2