CODEWITHSUNDEEP
pythoncaesar-cipher
Lanie909
Lanie909

Reputation: 919

Caesar Cipher Python

In the first For Loop below, the code successfully shifts the letters num places to the right. The issue is in the second For Loop, it doesn't reverse it completely like it's supposed to. I've included output below. Any advice would be appreciated. Thanks 

def cipher(message):
num = int(input())
final = []
finalReverse = []
for i in message:
        if i.isalpha():
                i = chr(ord(i)+num)
                final.append(i)
        if not i.isalpha():
                final.append(i)
final = ''.join(map(str, final))
print(final)
for i in final:
        if chr(ord(i)-num).isalpha:
                x = chr(ord(i)-num)
                finalReverse.append(x)
        if not chr(ord(i)).isalpha:
                finalReverse.append(char(ord(i)))
finalReverse = ''.join(map(str, finalReverse))
print(finalReverse)

cipher("The New York Times is in New York City.")

OUTPUT: (i entered number 3 for num)

1st For Loop's Output: Wkh Qhz \run Wlphv lv lq Qhz \run Flw||.

2nd For Loop's Output: TheNewYYorkTimesisinNewYYorkCityy+

Expected 2nd For Loop's Output: The New York Times is in New York City.

Upvotes: 1

Views: 356

Answers (2)

glibdud
glibdud

Reputation: 7840

There are several problems here.

You should be using else.

You follow if <condition>: with if not <condition>:. Instead, use else:

if i.isalpha():
    i = chr(ord(i)+num)
    final.append(i)
else:
    final.append(i)

This isn't just cosmetic... since you change i in the if block, it's possible for both the if and if not blocks to run in a single iteration. Using else solves this (and is better style anyway).

You forgot to call isalpha in the decrypt section

You need to add parens to the end of your isalpha calls in the decrypt section, otherwise only the if block will ever run (because a method or function object is always considered true).

if chr(ord(i)-num).isalpha():
    ...

You used the wrong variable in your decrypt else loop

You're appending x to the list in the decrypt section's else block, but x only makes sense in the if block. Use i.

if chr(ord(i)-num).isalpha():
    x = chr(ord(i)-num)
    finalReverse.append(x)
else:
    finalReverse.append(i)

Fixing those should produce your original message successfully.

Upvotes: 1

anurag0510
anurag0510

Reputation: 763

The answer is pretty simple. In first loop you didn't performed any conversion on spaces.

if not i.isalpha(): 
    final.append(i)

But in second loop you are trying to convert spaces before appending to decryption list.

if not chr(ord(i)-num).isalpha:           
    finalReverse.append(x)

Also you are again appending x which is the value from upper condition .

finalReverse.append(x)

Instead of this you just have to append original value.

if not chr(ord(i)).isalpha: 
    finalReverse.append(char(ord(i)))

Let me know if you still have an issue.

Upvotes: 0

Related Questions