Replace all words from word list with another string in python

Question

I have a user entered string and I want to search it and replace any occurrences of a list of words with my replacement string.

import re

prohibitedWords = ["MVGame","Kappa","DatSheffy","DansGame","BrainSlug","SwiftRage","Kreygasm","ArsonNoSexy","GingerPower","Poooound","TooSpicy"]


# word[1] contains the user entered message
themessage = str(word[1])    
# would like to implement a foreach loop here but not sure how to do it in python
for themessage in prohibitedwords:
    themessage =  re.sub(prohibitedWords, "(I'm an idiot)", themessage)

print themessage

The above code doesn't work, I'm sure I don't understand how python for loops work.

Answer 1

You can do that with a single call to sub:

big_regex = re.compile('|'.join(map(re.escape, prohibitedWords)))
the_message = big_regex.sub("repl-string", str(word[1]))

Example:

>>> import re
>>> prohibitedWords = ['Some', 'Random', 'Words']
>>> big_regex = re.compile('|'.join(map(re.escape, prohibitedWords)))
>>> the_message = big_regex.sub("<replaced>", 'this message contains Some really Random Words')
>>> the_message
'this message contains <replaced> really <replaced> <replaced>'

Note that using str.replace may lead to subtle bugs:

>>> words = ['random', 'words']
>>> text = 'a sample message with random words'
>>> for word in words:
...     text = text.replace(word, 'swords')
... 
>>> text
'a sample message with sswords swords'

while using re.sub gives the correct result:

>>> big_regex = re.compile('|'.join(map(re.escape, words)))
>>> big_regex.sub("swords", 'a sample message with random words')
'a sample message with swords swords'

As thg435 points out, if you want to replace words and not every substring you can add the word boundaries to the regex:

big_regex = re.compile(r'\b%s\b' % r'\b|\b'.join(map(re.escape, words)))

this would replace 'random' in 'random words' but not in 'pseudorandom words'.

Answer 2

try this:

prohibitedWords = ["MVGame","Kappa","DatSheffy","DansGame","BrainSlug","SwiftRage","Kreygasm","ArsonNoSexy","GingerPower","Poooound","TooSpicy"]

themessage = str(word[1])    
for word in prohibitedwords:
    themessage =  themessage.replace(word, "(I'm an idiot)")

print themessage