Get characters after a word in Python

Question

I've been trying for hours to do this in Python and I don't know what else to do. I have a string similar to this:

title = "Marielizabeth's Diary Chapter 9"

I want to get the number after the word "chapter" and then put a 0 in front of it: "Marielizabeth's Diary Chapter 09". I can't use title.replace because I don't know what I'll get. I only know that the number is after the word "chapter".

chapter = title.split('Chapter ', 1)
for char in chapter:
 print char

But it doesn't work. How can I do this?

Final solution:

title = "Marielizabeth's Diary Chapter 9"
re.sub('Chapter (\d$)', lambda m: "0" + m.group(1), title)

Gary Walker · Accepted Answer · 2014-05-31 05:39:36Z

2

If your problem statement is 100% accurate, there is a very simple way, use the replace method and replace "Chapter " with "Chapter 0"

e.g.

title = "Marielizabeth's Diary Chapter 9"
title = title.replace("Chapter ", "Chapter 0")

This depends upon a single space between chapter and the following number, i.e., an exact match to your problem statement.

edited May 31, 2014 at 5:39

answered May 31, 2014 at 5:33

Gary Walker

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10 Comments

Dair Over a year ago

"I can't use title.replace because I don't know what I'll get." -OP

alecxe Over a year ago

This is a nice answer, though still not sure if Chapter 10 should be replaced with Chapter 010. Probably the OP wants to "catch" a single digit only.

Jesús León Over a year ago

Thanks to everyone for their answers! Yes, I need to replace it only if it's single digit.

Gary Walker Over a year ago

Yes, I answered this after the regex based answer by you (alecxa) was already posted -- a certainly more general approach. It is just that clever use of replace can be an incredibly simple and fast solution sometimes that people overlook because regex is potent. Problem definition is definitely the key to writing the correct solution.

alecxe Over a year ago

@GaryWalker yeah, seeing a bigger picture :)

|

alecxe · Accepted Answer · 2014-05-31 05:31:50Z

1

You can pass a function inside the repl argument of re.sub():

>>> import re
>>> title = "Marielizabeth's Diary Chapter 9"
>>> re.sub('Chapter (\d)', lambda m: "0" + m.group(1), title)
"Marielizabeth's Diary 09"

Here (\d) is a capturing group that matches a single digit.

answered May 31, 2014 at 5:31

alecxe

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2 Comments

Martin Konecny Over a year ago

You don't necessarily need the (\d+) instead of (\d). Both will match "Chapter 9"

alecxe Over a year ago

@MartinKonecny yup, wasn't sure about whether match one or multiple digits, let's see what the OP would say. Thanks.

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