2
\$\begingroup\$

Currently, I have this and it's working for all cases:

import math
import os
import random
import re
import sys

def caesarCipher(s, k):
    st = []
    for i in range(0,len(s)):
        if 65<=ord(s[i])<=90: 
            temp = ord(s[i])+k%26
            if (temp>90):
                temp-=26
            st.append(chr(temp))
        elif 97<=ord(s[i])<=122:
            temp = ord(s[i])+k%26
            if (temp>122):
                temp-=26
            st.append(chr(temp))   
        else: st.append(s[i])
    return ''.join(st)




if __name__ == '__main__':

    s = input()

    k = int(input())

    result = caesarCipher(s, k)

I'm not sure if the multiple if loops reduce readability. Is there a cleaner way to do this?

Sample I/O:

Input: s = middle-Outz , k=2
Output: s = okffng-Qwvb

Input: s = Always-Look-on-the-Bright-Side-of-Life ; k=5
Output: s = Fqbfdx-Qttp-ts-ymj-Gwnlmy-Xnij-tk-Qnkj
\$\endgroup\$
3
\$\begingroup\$

Review

  • Remove unused imports

    You don't use any of these imports, just remove them to reduce clutter

  • Read PEP8 the python style guide

    1. Functions and variables should be snake_case
    2. There should be a <space> in between operators
  • Instead of appending to a list, you could create the string for the start

    So instead of making st = [], do st = '' and st += char, no need to join then

    However you could make the shifting a separate function, and then ''.join() becomes needed again

  • When looping, loop over the item not the index

    Instead of for i in range(len(s)) you could directly loop over the char --> for i in s

  • There is a function to determine if we encounter an uppercase or lowercase

    You could use char.isupper() or char.islower()

  • Simplify the shifting

    You could use the fact that if you subtract the start ord('a') or ord('A') and then modulo, the extra check of if temp > x becomes not needed

  • Notice how the operations for each case (upper, lower) are mostly similar

Putting it all together

import string
APLHA_LEN = len(string.ascii_lowercase)

def shift_letter(letter, shift):
    start = ''
    if letter.isupper():
        start = ord('A')
    elif letter.islower():
        start = ord('a')
    return chr((ord(letter) - start + k) % APLHA_LEN + start) if start else letter

def ceasar_cipher(st, shift):
    return ''.join(shift_letter(letter, shift) for letter in st)

BUT, there is a better way...

As mentioned by someone already you could use the maketrans function very nicely for ceasar ciphers.

Giving you something like this

from string import ascii_lowercase as lc, ascii_uppercase as uc

def ceasar_cipher_translate(st, k):
    trans = str.maketrans(lc + uc, lc[k:] + lc[:k] + uc[k:] + uc[:k])
    return str.translate(st, trans)

NOTE That this code assumes Python3.x

\$\endgroup\$
  • \$\begingroup\$ A magic number 26 is still lingering. Consider something along the lines of len(string.ascii_lowercase). \$\endgroup\$ – vnp Sep 18 '18 at 20:11
  • \$\begingroup\$ @vnp Done, that slipped my mind :) \$\endgroup\$ – Ludisposed Sep 19 '18 at 13:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.