Checking "encryption" and "decryption" of Caesar Cipher using strings in python

Question

I was supposed to create strings in my python function to show that the encryption and decryption of my code was working properly. Below is my code.

def encrypt1():
    plain1 = input('Enter plain text message: ')
    cipher = ''

    for each in plain1:
        c = (ord(each)+3) % 126

        if c < 32: 
            c+=31

    cipher += chr(c)

    print ("Your encrypted message is:" + cipher)

encrypt1()

1.) I get the "Inconsistent use of tabs and spaces" error

2.) How should I input set, constant strings to get the wanted input check if my code works (for example, type in meet and get the correct input, etc)

you just have to indent this line `cipher += chr(c)`. Also, passing argument `plain1` to the function doesn't make sense since you overwrite it using `input()`. The python versions have nothing to do with this — Ma0, Sep 14 '16 at 14:44

gowrath · Answer 1 · 2016-09-14T15:11:23.633

Your code is mostly fine but there are a few issues that I've pointed out:

Your indenting is off. The line cipher += chr(c) should be indented to match the things in the for loop
The function encypt1() shouldn't take a parameter; you are setting plain1 in the method itself so you can declare it there
If you want to deal with just lowercase letters, you should be doing % 123 (value of 'z') and the if clause should check if c < 97. If you want to wrap around printable ascii what you're doing is fine.

This gives:

    def encrypt1():
        plain1 = input('Enter plain text message: ')
        cipher = ''
        for each in plain1:
            c = (ord(each)+3) % 126
            if c < 32: 
                c+=31
            cipher += chr(c)
        print ("Your encrypted message is:" + cipher)

Because you want to be able to test this on multiple strings, you would want to pass plain1 as a parameter to the function. But you also want the user to be able to input plain1 if a parameter isn't passed in to the function. For that I would suggest a default parameter. Look at the commented code below:

def encrypt1(plain1=""):        # if no argument is passed in, plain1 will be ""
    if not plain1:              # check if plain1 == "" and if so, read input from user
        plain1 = input('Enter plain text message: ')
    cipher = ''
    for each in plain1:
        c = (ord(each)+3) % 126
        if c < 32: 
            c+=31
        cipher += chr(c)
    return cipher               # rather than printing the string, return it instead

So to test this you could do:

test_strings = ['hello world', 'harambe', 'Name', 'InputString']

for phrase in test_strings:
    print ("Your encrypted message is:" + encrypt1(phrase))

Which gives the output:

Your encrypted message is:khoor#zruog
Your encrypted message is:kdudpeh
Your encrypted message is:Qdph
Your encrypted message is:LqsxwVwulqj

Your answer solves my error problems, but I still don't know how to input the strings :p — Yeo Zhe Yong, Sep 14 '16 at 15:02
@YeoZheYong Ah I just saw the edit to your question. What do you mean input the strings? Do you want a way to test this on multiple strings somehow? — gowrath, Sep 14 '16 at 15:03
yes, sorry if I'm making a fool of myself, but our university module mostly involves html and javascript, with only a little bit of python, so inexperienced people like me end up rather confused when python/php questions come out — Yeo Zhe Yong, Sep 14 '16 at 15:07
@YeoZheYong No worries, I've updated my answer. Let me know if I understood your question correctly and feel free to ask for clarification. — gowrath, Sep 14 '16 at 15:11
you can also use `plain1 = plain1 or input('Enter plain text message: ')` since `or` shortcircuits. Also +1 for test string 'harambe' — Ma0, Sep 14 '16 at 15:13

Checking "encryption" and "decryption" of Caesar Cipher using strings in python

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