CODEWITHSUNDEEP
pythonencryption
user2816683
user2816683

Reputation: 47

could someone please explain this simple python code?

I am a few weeks into GCSE Computing, and I am in year 9. Today we went through a program that was a simple encryption program. I didn't really understand it that much. Could an experienced python programmer please explain this piece of code, simply?

BTW - I have put a comment by the pieces of code I understand.

message = str(input("Enter message you want to encrypt: ")) #understand
ciphered_msg = str() #understand
i = int() #understand
j = int() #understand
n = int(3)

for i in range(n):
    for j in range(i, len(message), n):
        ciphered_msg = ciphered_msg + message[j]

print(ciphered_msg) #understand

Please help me with this, as I would really like some more python knowledge and to get an A* in my exam.

I know how a for loop works, but I just don't understand how this one works.

Thanks!

Upvotes: 1

Views: 238

Answers (1)

Óscar López
Óscar López

Reputation: 235984

These lines are un-Pythonic and you should not do this:

ciphered_msg = str()
i = int()
j = int()
n = int(3)

Instead do this, it's completely equivalent code but simpler and clearer:

ciphered_msg = ""
i = 0 # unnecessary, the i variable gets reassigned in the loop, delete this line
j = 0 # unnecessary, the j variable gets reassigned in the loop, delete this line
n = 3

The loop is doing the following: starting in 0, then 1 and finally 2, it takes every third index in the message's length and accesses the corresponding position in the message array, appending the character at that position and accumulating the result in the ciphered_msg variable. For instance, if message is of length 5, the indexes in message will be accessed in this order:

0 3 1 4 2

So basically we're scrambling the characters in the input message - for example, if the input is abcde the output will be adbec. This is a very weak cipher, it's only transposing the characters:

# input
0 1 2 3 4 # original indexes
a b c d e # `message` variable

# output
0 3 1 4 2 # scrambled indexes
a d b e c # `ciphered_msg` variable

Upvotes: 3

Related Questions