Cryptography: ciphering in python

Question

Problem statement: Every upper case alphabet shifts to the left, for example if the alphabet D was left shifted by 3, it will become A, and E would become B, and so on..

I got the first two test cases correctly, but I got stuck at the third one that had a pound sign.

My trial:

sh = int(input())
s = input()
n = ""
for char in s:
    val = ord(char)-sh
    if char != " ":
        if 65 <= val <= 90:
            n += chr(val)
        else:
            if val < 65:
                if '0' <= char <= '9':
                    n += char
                else:
                    n += chr(90 - (65 - val - 1))
    else:
        n += char
print(n)

Test case 1:

(in1)>> 3
(in2)>> H3LL0 W0RLD
(out)>> E3II0 T0OIA

Test case 2:

(in1)>> 6
(in2)>> THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
(out)>> NBY KOCWE VLIQH ZIR DOGJM IPYL NBY FUTS XIA

Test case 3:

(input_num_1)>> 2
(input_num_2)>> H4IGDFDNO£PJNHVDKHZPDOPG2
(ExpectedOut)>> F4GEBDBLM\-62\-93NHLFTBIFXNBMNE2
(My_output_.)>> F4GEBDBLMNHLFTBIFXNBMNE2

Your help & and time to review this is seriously appreciated. Thank you.

Edit: To add more clarity, I've added what my code yields as an output under the expected output, and to be specific, how/why is £ mapped to \-62\-93 ?

A pound sign: (£) is U+00A3 in Unicode. When written in UTF-8 that is 0xC2 0xA3, which is what you are seeing, converted to signed base 10. — rossum
– rossum, Commented Aug 2, 2020 at 10:37
Yeah I figured, I added this conversion bit to the code and it works now, Thanks mate! — Ahmed Alhallag
– Ahmed Alhallag, Commented Aug 4, 2020 at 2:16

JimmyCarlos · Accepted Answer · 2020-08-02 05:36:11Z

3

Can't beat a good Caesar Cipher question. You're on the right track but I would use inbuilt checks on the character to quickly decide what to do with it.

sh = int(input())
s = input()
n = ""
for char in s:
    val = ord(char)-sh
    if char.isupper() and char.isalpha():
        if 65 <= val <= 90:
            n += chr(val)
        else:
            n += chr(90 - (65 - val - 1))
    else:
        n += char
print(n)

answered Aug 2, 2020 at 5:36

JimmyCarlos

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1 Comment

Ahmed Alhallag Over a year ago

Thanks pal! I'll consider this of course! note that I've added an Edit that includes the exact part that I cannot match (the pound sign).

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