Python shuffle the middle letters in all the words of a sentence

Question

The purpose of the program is to shuffle only the middle letters of each word in a sentence, leaving it still readable like this:

Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae.

def garble(sentence):

    return ' '.join([word[0] + ''.join(random.sample([char for char in word[1:-1]],len(word[1:-1]))) + word[-1] if len(word) > 1 else word for word in  sentence.split()])

I definitely think I have gone overboard putting it all in one line but I'm not sure where to separate it

Answer 1

I totally agree with @alecxe's comment on Python, but I thing regex is a little overkill for this problem. So, here's a non-regex solution:

import random

def shuffle_string(string):
    chars = list(string)
    random.shuffle(chars)
    return ''.join(chars)

def garble_word(word):
    # No operation needed on sufficiently small words
    # (Also, main algorithm requires word length >= 2)
    if len(word) <= 3:
        return word

    # Split word into first & last letter, and middle letters
    first, mid, last = word[0], word[1:-1], word[-1]

    return first + shuffle_string(mids) + last

def garble(sentence):
    words = sentence.split(' ')
    return ' '.join(map(garble_word, words))

Edit: It should be noted that while my solution is simpler than @alecxe's, it is not as robust. If you care about dealing with strange whitespace properly, or about handling punctuation (see @RolandIllig's comment), use @alecxe's solution.

Answer 2

The fact that Python allows fitting things on a single line and pack in comprehensions, does not mean you need to try to squash the code to be shorter hurting readability. I would probably at least expand the code into multiple lines with descriptive variable names.

Here is, though, an alternative solution based on regular expression replacement function:

from random import shuffle
import re


RE_GARBLE = re.compile(r"\b(\w)(\w+)(\w)\b")


def garble_word(match):
    first, middle, last = match.groups()

    middle = list(middle)
    shuffle(middle)

    return first + ''.join(middle) + last


def garble(sentence):
    return RE_GARBLE.sub(garble_word, sentence)

Answer 3

You definitely need to split up the line. Something like the following is way more readable.

def garble(sentence):
    words = []
    for word in  sentence.split():
        if len(word) > 1:
            words.append(word[0]
                       + ''.join(random.sample(
                         [char for char in word[1:-1]], len(word) - 2))
                       + word[-1])
        else:
            words.append(word)
    return ' '.join(words)