problems with int() in a python encryption programm

Question

I need to make sure that the input shift for the cypher is a integer. How would I go around making sure that it is, so far when ever I use the int() variable round any of the inputs, it generates an error even when I do put an integer in.

Here is the code, it is written and compiled with 2.7.6

 import re

def caesar(plain_text, shift):
    cipherText = ''
    for ch in plain_text:
      stayInAlphabet = ord(ch) + shift
      if ch.islower():
        if stayInAlphabet > ord('z'):
          stayInAlphabet -=26
        elif stayInAlphabet < ord('a'):
          stayInAlphabet += 26
      elif ch.isupper():
        if stayInAlphabet > ord('Z'):
          stayInAlphabet -= 26
        elif stayInAlphabet < ord('A'):
          stayInAlphabet += 26
      finalLetter = chr(stayInAlphabet)
      cipherText += finalLetter
    print(cipherText)
    return cipherText

selection = input ("encrypt/decrypt ")
if selection == 'encrypt':
  plainText = input("What is your plaintext? ")
  shift = (int(input("What is your shift? ")))%26
  caesar(plainText, shift)

else:
  plainText = input("What is your plaintext? ")
  shift = ((int(input("What is your shift? ")))%26)*-1
  caesar(plainText, shift)

Hi Alexander! It will help people answer your question if you post the error — fdsa, Apr 24 '15 at 14:12

score 2 · Accepted Answer · edited May 23 '17 at 12:06

2

For python 2.7, you want to use raw_input instead of input. See this post for more detail.

edited May 23 '17 at 12:06

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answered Apr 24 '15 at 14:09

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problems with int() in a python encryption programm

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