Restarting code in Python 3.1

Question

I've looked through a few answers on here but none have worked for me, and I know there's probably a lot of things wrong with this code, but all I want to know is how to simply restart the code if the input at the END is 'Yes'

Code = input("Do you want to encrypt or decrypt? ")
Code = Code.upper()
Answer = ["ENCRYPT","DECRYPT"]

    if Code in Answer:

            Plaintext = input("What's your message? ")
            Plaintext = Plaintext.upper()
            Shift = int(input("What's the shift number? "))
            LengthPT = len(Plaintext)
            CodeLetter = ""

            if Code == ("ENCRYPT"):
                    for i in range (0,LengthPT):
                            Pletter = ord(Plaintext[i]) -64
                            Codeletter = Pletter + Shift
                            if Codeletter > 26:
                                    Codeletter = Codeletter - 26
                            Codeascii = chr(Codeletter + 64)
                            CodeLetter = CodeLetter + Codeascii

            elif Code == ("DECRYPT"):
                    for i in range (0,LengthPT):
                            Pletter = ord(Plaintext[i]) -64
                            Codeletter = Pletter - Shift
                            if Codeletter < 0:
                                    Codeletter = Codeletter + 26
                            Codeascii = chr(Codeletter + 64)
                            CodeLetter = CodeLetter + Codeascii
    else:
            print("Wrong answer.")

    if Code == ("ENCRYPT"):
            print("Encoded Message =", CodeLetter)

    elif Code == ("DECRYPT"):
            print("Decoded Message =", CodeLetter)

    Answer2 = input("Do you want to restart? (Yes/No): ")

If none of the existing answers have helped, how do you expect another one to? Use a loop. — jonrsharpe, Apr 25 '16 at 10:57
Because there might be somebody who knows an answer that I haven't seen yet, which might just work. — Connor, Apr 25 '16 at 11:42
Python lacks any sort of "Go to" statement, the best you can get is a loop. — Tadhg McDonald-Jensen, Apr 26 '16 at 20:04
Possible duplicate of [Python - How to make program go back to the top of the code instead of closing](http://stackoverflow.com/questions/18791882/python-how-to-make-program-go-back-to-the-top-of-the-code-instead-of-closing) — Tadhg McDonald-Jensen, Apr 26 '16 at 20:10

score 3 · Accepted Answer · answered Apr 25 '16 at 11:00

3

There are many ways, but this seems to be the shortest path:

Answer2 = "Yes"
while Answer2 == "Yes":
  ...
  Answer2 = input("Do you want to restart? (Yes/No): ")

Typically you might want to .lower ().strip () Answer2 too.

answered Apr 25 '16 at 11:00

gauteh

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Typically you'll want to get rid of the extra variable and just use a `while True:` loop. Then you `break` out of the loop if the answer is not "Yes". – Matthias Apr 25 '16 at 11:22
@gauteh Could you possibly provide an example of that solution added into the entire code, with the ellipse part filled in please? I neglected to mention that I'm quite new to all of this, so I'm not entirely sure how to implement your solution. – Connor Apr 28 '16 at 13:13
@Connor: You put all of your code in where the ellipsis is. And then fix the second Answer2-line if necessary. Experiment a bit with extremely simple `while` loops if that doesn't work (e.g. change the ellipsis to print ("a")). – gauteh Apr 28 '16 at 13:27
Thank you, I finally figured it out and got it working. Thanks for the help :) – Connor Apr 28 '16 at 13:49

score -1 · Answer 2 · answered Apr 25 '16 at 11:01

-1

Make it all a function. Check if the answer is 'yes' and then call the function again. Recursion is fine in Python, so this will work.

answered Apr 25 '16 at 11:01

TKoL

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Recursion is not fine in Python and using functions as jump marks is wrong in every language. – Matthias Apr 25 '16 at 11:21
Python (sadly) does not have tail-call-optimization https://en.wikipedia.org/wiki/Tail_call .. So making the function recursive will limit you to the default stack size.. You can ofc use ugly hacks like trampoline techniques.. However, using recursion in Python feels like working against the language rather than with the language. – Michelrandahl Apr 25 '16 at 15:11
Thank you @Matthias and Mitzh , I didn't realize recursion was considered so bad in python. – TKoL Apr 26 '16 at 13:02

Restarting code in Python 3.1

2 Answers2