Regex to find last word in a string (Python)

Question

I am trying to write a simple regex that finds if the last word in the string is a specific one.

I wrote something like this "(\W|^)dog$". (Check if last word in the sentence is dog)

This regex is correct but in python it is returning nothing when i type something like "I like dog".

I tested this in the Rubular regex editor and it seems to work.

Am I doing something wrong ?

EDIT : Adding my simple code

import re
pm = re.compile("(\W|^)dog$")
has = pm.match("i love dog")
print(has)

Yes. NO hypenated word required> Also FYI I tried ( |^)dog$ with same result !!! — rajaditya_m
– rajaditya_m, Commented Oct 18, 2013 at 16:22
possible duplicate of What is the difference between Python's re.search and re.match? — Ashwini Chaudhary
– Ashwini Chaudhary, Commented Oct 18, 2013 at 16:26
df.str.replace(r"(\W|^)(dog|cat)$", ' ') this worked for a list of terms in python pandas — citynorman
– citynorman, Commented Apr 7, 2022 at 2:24

Rohit Jain · Accepted Answer · 2013-10-18 16:30:33Z

20

You don't need to regex here. Simple split will do the job:

>>> s = "I like dog"
>>> s.rsplit(None, 1)[-1] == 'dog'
True

Since you need the last word only, str.rsplit can be used to start splitting from end, and passing 1 as 2nd argument, will only perform split only once. Then get the last element of the returned list.

As for doing this with regex, you would need to use re.search method, instead of re.match method. The later one matches at the beginning of the string, so you would need to build the regex to match the entire string. You can rather do:

pm = re.compile(r"\bdog$")
has = pm.search("i love dog")

\b is word boundary. See Live Demo.

To do the same with re.match, your regex should be - r".*dog$".

pm = re.compile(r".*dog$")
has = pm.match("i love dog")

edited Oct 18, 2013 at 16:30

answered Oct 18, 2013 at 16:23

Rohit Jain

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5 Comments

rajaditya_m Over a year ago

Thank you Mr. Jain. But this simple regex is my way of revising regular expressions for upcoming interviews and hence I am interested to know how to do it via python.

Rohit Jain Over a year ago

@rajaditya_m You should use re.search method instead of re.match.

rajaditya_m Over a year ago

Awesome. I just changed the match to search in my OLD regex and it also works. (In this case atleast).

Hannele Over a year ago

r".*dog" would match stuff like 'asdfasdfdog', no? The word boundary might still be desired.

Ilya Libin Over a year ago

I the question was about the regex and not the alter solutions, so i't is good to know what the regex is for this case

user1120144 · Accepted Answer · 2013-10-18 16:30:24Z

2

Here's a slight modification of your code (that works):

import re
pm = re.compile(r'.*\b(dog)$')
has = pm.match("i love dog")
print(has)

The regex .*\b(dog)$ maches anything (.*) then a word boundry (\b) and then your word (dog) and then the end of the line ($). Which is exactly what you want. Live demo here.

answered Oct 18, 2013 at 16:30

user1120144

Comments

cad106uk · Accepted Answer · 2016-01-20 15:59:10Z

1

Get the word at the end of the string. Whatever that word is.

import re
pattern = re.compile(r"(\w+)$")
has = pm.search("i love dog")
print has.group(0)

answered Jan 20, 2016 at 15:59

cad106uk

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Comments

Baboucarr Badjie · Accepted Answer · 2022-12-21 19:30:40Z

1

You can do

import re
text = "Python was conceived in the late 1980"
s = re.findall(r"\s(\w+)$", text)
print(s)

Or

s = re.split("\s", text)
print(s[-1])

answered Dec 21, 2022 at 19:30

Baboucarr Badjie

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