Reverse words in string - same order - including whitespace

Question

I am trying to reverse the letters of each words contained in a given string, keeping the same word order and also keeping the same whitespace.

So 'This is an example!' should return: 'sihT si na !elpmaxe' (note two spaces between each word).

The solution I wrote doesn't deal with this whitespace:

def reverse_words(str1):
    list1 = str1.split()
    list2 = []
    for e in list1:
        e = e[::-1]
        list2.append(e)
    return ' '.join(list2)

That should be `.split(' ')`, as without an argument consecutive whitespace is grouped into one. Also, don't name your own object `str`. — jonrsharpe, Jan 25 '15 at 12:57
@jonrsharpe replaced str by str1. So if I do .split(' ') won't it return 2 whitespaces even if the original string only contains 1 space after each word? — David B., Jan 25 '15 at 13:09
Fair point, tried it with your solution below and it worked. Thanks! — David B., Jan 25 '15 at 13:15

score 7 · Answer 1 · edited Jan 25 '15 at 13:01

7

If you want to preserve white space then use regex:

>>> import re
>>> s = 'This is an example!'
>>> re.sub(r'\S+', lambda m:m.group(0)[::-1], s)
'sihT si na !elpmaxe'
>>> s = 'This is an    example!'
>>> re.sub(r'\S+', lambda m:m.group(0)[::-1], s)
'sihT si na    !elpmaxe'

edited Jan 25 '15 at 13:01

falsetru

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answered Jan 25 '15 at 12:58

Ashwini Chaudhary

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how about this `" ".join(w[::-1] for w in re.split("\s", 'This is an example!'))` – Grijesh Chauhan Jan 25 '15 at 13:03
@GrijeshChauhan This one is slight fast, but speed wise Jon's solutions is the best. – Ashwini Chaudhary Jan 25 '15 at 13:11
Good decision! Thank you – Mikhail Barinov Aug 15 '21 at 13:53

jonrsharpe · Accepted Answer · 2015-01-25T13:17:36.387

6

To do it without regular expressions, note that str.split will group consecutive whitespace when called without an explicit argument. To avoid that, specifically split on spaces. Note that you can shorten the whole function using a list comprehension:

def reverse_words(string): # don't name your own object str
    return ' '.join([word[::-1] for word in 
                     string.split(' ')])

edited Jan 25 '15 at 13:17

answered Jan 25 '15 at 13:07

jonrsharpe

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1

I think simpler one , but `word[::1]` should be `word[::-1]` – Grijesh Chauhan Jan 25 '15 at 13:09
2

This takes *779 µs* compared to my solution's *1.91 ms* for a string for length 3000. *+1*. – Ashwini Chaudhary Jan 25 '15 at 13:10
@ha9u63ar that's really not helpful – jonrsharpe Jan 25 '15 at 13:14

Reverse words in string - same order - including whitespace

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