Python letter swapping

Question

I'm making a program that scrambles words for fun and I've hit a roadblock. I am attempting to switch all the letters in a string and I'm not quite sure how to go about it (hello = ifmmp). I've looked all around and haven't been able to find any answers to this specific question. Any help would be great!

I'm trying to replace the whole alphabet though, that doesn't touch on it from what I've seen. — RyanMcCue, Oct 29 '13 at 23:26
Seems like a duplicate of http://stackoverflow.com/questions/2400504/easiest-way-to-replace-a-string-using-a-dictionary-of-replacements — Moshe, Aug 26 '15 at 16:17

score 0 · Answer 1 · answered Oct 29 '13 at 23:26

You want a simple randomized cypher? The following will work for all lowercase inputs, and can easily be extended.

import random
import string

swapped = list(string.lowercase)
random.shuffle(swapped)
cipher = string.maketrans(string.lowercase, ''.join(swapped))

def change(val):
    return string.translate(val, cipher)

score 0 · Answer 2 · answered Oct 29 '13 at 23:26

You can probably modify this example to achieve what you need. Here every vowel in a string is replaced by its vowel position:

from string import maketrans   # Required to call maketrans function.

intab = "aeiou"
outtab = "12345"
trantab = maketrans(intab, outtab)

str = "this is string example....wow!!!";
print str.translate(trantab);


# this is the output
"th3s 3s str3ng 2x1mpl2....w4w!!!"

score 0 · Answer 3 · answered Oct 29 '13 at 23:50

Try maketrans in combination with the string.translate function. This code removes letters from your word from the letters you are scrambling with first. If you just want lowercase only use string.lowercase instead of string.letters.

>>> import string, random
>>> letters = list(string.letters)
>>> random.shuffle(letters)
>>> letters = "".join(letters)
>>> word = 'hello'
>>> for letter in word:
...     letters = letters.replace(letter, '')
...
>>> transtab = string.maketrans(word, letters[:len(word)])
>>> print word.translate(transtab)
XQEEN

score 0 · Answer 4 · answered Oct 30 '13 at 02:39

The "scrambling" you appear to be after is called Caesar's cipher, with a right shift of 1. The following Python will achieve what you're after:

def caesar(str):
  from string import maketrans
  fromalpha = "abcdefghijklmnopqrstuvwxyz"
  # Move the last 1 chars to the start of the string
  toalpha = fromalpha[1:] + fromalpha[:1]
  # Make it work with capital letters
  fromalpha += fromalpha.upper()
  toalpha += toalpha.upper()
  x = maketrans(fromalpha, toalpha)
  return str.translate(x)

If you're interested in the general case, this function will do the job. (Note that it is conventional to express Caesar ciphers in terms of left shifts, rather than right.)

def caesar(str, lshift):
  from string import maketrans
  fromalpha = "abcdefghijklmnopqrstuvwxyz"
  toalpha = fromalpha[-lshift:] + fromalpha[:-lshift]
  fromalpha += fromalpha.upper()
  toalpha += toalpha.upper()
  x = maketrans(fromalpha, toalpha)
  return str.translate(x)

Python letter swapping

4 Answers4