Replace command condition for replacing strings

Question

Want to replace a certain words in a string but keep getting the followinf result:

String: "This is my sentence."

User types in what they want to replace: "is"

User types what they want to replace word with: "was"

New string: "Thwas was my sentence."

How can I make sure it only replaces the word "is" instead of any string of the characters it finds?

Code function:

import string
def replace(word, new_word):
   new_file = string.replace(word, new_word[1])
   return new_file

Any help is much appreciated, thank you!

Good find. I searched for a duplicate but with the "replace" term, not "find". — Jean-François Fabre, Nov 17 '16 at 20:50
so did I: [python replace words not partial words](https://www.google.ca/search?client=safari&rls=en&q=python+replace+words+not+partial+words&oq=python+replace+words+not+partial+words&gs_l=serp.3...44021.51387.0.51523.33.30.0.3.3.0.127.2123.23j5.28.0....0...1c.1.64.serp..2.18.1097...0j0i67k1j0i131k1j0i22i30k1j33i21k1.0mLcUwAiDdk). I think the term "not partial word" was the key here. — Tadhg McDonald-Jensen, Nov 17 '16 at 20:52
@TadhgMcDonald-Jensen the trick is to google the keywords, just that I'm forgetting everytime. SO engine is good because you can filter tags using sqbrackets, but google is better for general search, and 99% of the time a SO answers pops up first! — Jean-François Fabre, Nov 17 '16 at 21:13

Jean-François Fabre · Accepted Answer · 2016-11-17T20:52:38.143

4

using regular expression word boundary:

import re

print(re.sub(r"\bis\b","was","This is my sentence"))

Better than a mere split because works with punctuation as well:

print(re.sub(r"\bis\b","was","This is, of course, my sentence"))

gives:

This was, of course, my sentence

Note: don't skip the r prefix, or your regex would be corrupt: \b would be interpreted as backspace.

edited Nov 17 '16 at 20:52

answered Nov 17 '16 at 20:46

Thank you so much! This was perfect for my program! – Jarred Nov 18 '16 at 01:47
1

@Jarred McMahan if an answer worked for you then please do accept it so that it is marked as 'Answered'. – Falloutcoder Nov 18 '16 at 13:26

Falloutcoder · Answer 2 · 2016-11-17T20:59:55.643

1

A simple but not so all-round solution (as given by Jean-Francios Fabre) without using regular expressions.

 ' '.join(x if x != word else new_word for x in string.split())

edited Nov 17 '16 at 20:59

answered Nov 17 '16 at 20:44

Falloutcoder

1

this wouldn't maintain the original whitespace since you are effectively replacing all whitespace with spaces. Also please give some info in your answer, just the single line of code isn't really all that helpful. – Tadhg McDonald-Jensen Nov 17 '16 at 20:50
@Jean: couldnt agree more. thanks for the hints and tip (y) – Falloutcoder Nov 17 '16 at 21:00
not so bad if you don't want to use regex. and pythonic as well. – Jean-François Fabre Nov 17 '16 at 21:12

2 Answers2