Question

Implement a function crypto() where every character at a odd position i in the alphabet will be encrypted with the character at position i+1 and every character at an even position i will be encrypted with the character at position i-1. Or like, ‘a’ is encrypted with ‘b’, ‘b’ with ‘a’, ‘c’ with ‘d’, ‘d’ with ‘c’, ‘e’ with ‘f’, ‘f’ with ‘e’, etc.

This should appear:

>>>>crypto('abc')

bad

>>>>crypto('OOZ')

PPY

***ATTEMPT

def crypto():
    return [ord(c) in s]
s = 'cat'
alist = ascii_list(s)
print alist

alist[0] +=1
alist[1] +=14

I’m almost positive I’m coming at this all wrong.

Answer 1

Here is what you want:

def crypto(s):
    return ''.join(chr(ord(c)+(1 if ord(c)%2 else -1)) for c in s)

EXPLANATION:

1. get the ordinal number for each character c in the string s (that’s for c in s part)
2. Notice that ord('a') and ord('A') are both odd (very useful!), so …
3. … (1 if ord(c)%2 else -1) part evaluates to 1 for odd ord(c) and -1 for even ones
4. add the value obtained above to the ord(c) and use chr to obtain the “encrypted” character
5. glue everything together with a ''.join()