String Manipulation Python

Question

I am trying to modify a string , by replacing each alphabet by an alphabet which is two postions ahead of it. e.g. 'a' replaced by 'c', 'b' replaced by 'd'. The only exceptions is 'y' should be replaced by 'a' and 'z' by 'b' (loops back to start).

I have written the following code for it, which seems to serve the purpose, but the output formatting kind of spoils it.

string = "g fmnc wms bgblr rpylqjyrc gr zw fylb."
print string
for i in string:
    if i.isalpha():
        if ord(i)>120:
            print chr(ord(i)-24),
        else:
            print chr(ord(i)+2),
    else: 
        print i

Output :

g fmnc wms bgblr rpylqjyrc gr zw fylb.
i   h o p e   y o u   d i d n t   t r a n s l a t e   i t   b y   h a n d .

Expected Output:

g fmnc wms bgblr rpylqjyrc gr zw fylb.
i hope you didnt translate it by hand.

Is there any alternative, quicker approach to solve this?

thanks did the following as an alternate approach intab = "abcdefghijklmnopqrstuvwxyz" outtab= "cdefghijklmnopqrstuvwxyzab" trantab = maketrans(intab, outtab) print string.translate(trantab) — misguided
– misguided, Commented Jul 23, 2013 at 0:33
This is called a Caesar cipher or shift cipher by the way. There are a bunch of questions on this on SO. — korylprince
– korylprince, Commented Jul 23, 2013 at 1:49

inspectorG4dget · Accepted Answer · 2013-07-23 00:19:20Z

3

The print i, syntax adds a space at the end of the thing that's being printed. You could solve this by putting all your characters in a list and ''.join()ing them in the end:

string = "g fmnc wms bgblr rpylqjyrc gr zw fylb."
print string
answer = []
for i in string:
    if i.isalpha():
        if ord(i)>120:
            answer.append(chr(ord(i)-24))
        else:
            answer.append(chr(ord(i)+2))
    else: 
        answer.append(i)
print ''.join(answer)

Of course, as others have suggested, string.translate will likely be far more straightforward

answered Jul 23, 2013 at 0:19

inspectorG4dget

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dawg · Accepted Answer · 2013-07-23 00:48:21Z

1

Here is a solution using string.translate:

from string import translate, maketrans, ascii_lowercase

s='g fmnc wms bgblr rpylqjyrc gr zw fylb.'

rot2=maketrans(
    ascii_lowercase,
    ascii_lowercase[2:]+ascii_lowercase[:2]
    )

print s.translate(rot2)

answered Jul 23, 2013 at 0:48

dawg

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Comments

seth · Accepted Answer · 2013-07-23 00:42:42Z

0

You can also use this horrific bastardization of a list comprehension.

message = "g fmnc wms bgblr rpylqjyrc gr zw fylb."
print message
print ' '.join([''.join([chr(((ord(letter)+2) % 122) + int(ord(letter)/121.0)*96) if ord(letter)>96 else letter for letter in word]) for word in message.split()])

answered Jul 23, 2013 at 0:42

seth

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