Reduce the length of words in a sentence

Question

This function's goal is to reduce the length of a sentence to exactly max_length characters by cutting each word in the sentence to a length of minimum 4 characters, if cutting each word to 4 characters isn't enough the the sentence is returned anyway.
All sentences are free of special characters and words are separated by spaces.
Here is the function:

def cut_everything(sentence, max_length):
    """
    reduces each word in sentence to a length of 4

    :type sentence: string
    :param sentence: the sentence to cut
    :type max_length: int
    :param max_length: the length to which the sentence will be reduced
    """
    words = sentence.split()
    for index, word in enumerate(words):
        word_length = len(word)
        if word_length > 4:
            to_cut = len(sentence) - max_length
            to_keep = word_length - to_cut
            if to_keep < 4:
                to_keep = 4
            words[index] = word[:to_keep]
            sentence = ' '.join(words)
            if len(sentence) <= max_length:
                break

    return sentence

My main concern for this review is performance, but any readability comment is appreciated

Answer 1

Review

• Magic numbers

  4 is a magic number, it is best to assign these to a variable name, that way it is more clear what this number means

  numbers don't have names, variables do

  MAX_WORD_LENGHT = 4
  

• Use built-ins when possible

  to_keep = word_length - to_cut
  if to_keep < 4:
  to_keep = 4
  

  Can be replaced with the max builtin

   to_keep = max(word_length - to_cut, 4)
  

• Add tests

  That way it becomes easy to check after a change if the function still works

Alternative

I went a slightly different route,

Instead of joining after each word, I calculate the chars we need to cut beforehand

So we can keep a variable that will hold the amount of chars we still need to cut to reach our target

And only at the return join the words

import doctest

MAX_WORD_LENGHT = 4

def cut_everything(sentence, max_length):
    """
    reduces each word in sentence to a length of 4

    :type sentence: string
    :param sentence: the sentence to cut
    :type max_length: int
    :param max_length: the length to which the sentence will be reduced

    >>> cut_everything('foo bar foooobar', 16)
    'foo bar foooobar'

    >>> cut_everything('foo bar foooobar', 8)
    'foo bar fooo'

    >>> cut_everything('foo bar foooobar baaarfoo', 20)
    'foo bar fooo baaarfo'

    >>> cut_everything('fooooooo baaaaaaar foooobar baaarfoo', 2)
    'fooo baaa fooo baaa'
    """
    words = sentence.split()
    chars_to_cut = len(sentence) - max_length
    for index, word in enumerate(words):
        if chars_to_cut < 0:
            break
        word_length = len(word)
        if word_length > MAX_WORD_LENGHT:
            to_keep = max(word_length - chars_to_cut, MAX_WORD_LENGHT)
            words[index] = word[:to_keep]
            chars_to_cut -= word_length - to_keep
    return ' '.join(words)

if __name__ == '__main__':
    doctest.testmod()