Python regex to match punctuation at end of string

Question

I need to match if a sentence starts with a capital and ends with [?.!] in Python.

EDIT It must have [?.!] only at end but allow other punctuation in the sentence

import re
s = ['This sentence is correct.','This sentence is not correct', 'Something is !wrong! here.','"This is an example of *correct* sentence."']

# What I tried so for is:
for i in s:
    print(re.match('^[A-Z][?.!]$', i) is not None)

It does not work, after some changes I know the ^[A-Z] part is correct but matching the punctuation at the end is incorrect.

Ludisposed · Accepted Answer · 2017-05-11T12:06:02.870

19

I made it working for myself, and just for clarification or if other people have the same problem this is what did the trick for me:

re.match('^[A-Z][^?!.]*[?.!]$', sentence) is not None

Explanation: Where ^[A-Z] looks for a Capital at start

'[^?!.]*' means everything in between start and end is ok except things containing ? or ! or .

[?.!]$ must end with ? or ! or .

edited May 11 '17 at 12:06

answered May 03 '17 at 08:40

Ludisposed

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Using a negative look-ahead followed by `.` is an intricate and probably inefficient way of achieving that. Consider using a negative character class: `[^?!.]*`. – lenz May 03 '17 at 08:49

Chankey Pathak · Answer 2 · 2017-05-03T07:43:52.477

2

Use the below regex.

^[A-Z][\w\s]+[?.!]$

Regex demo: https://regex101.com/r/jpqTQ0/2

import re
s = ['This sentence is correct.','this sentence does not start with capital','This sentence is not correct']

# What I tried so for is:
for i in s:
    print(re.match('^[A-Z][\w\s]+[?.!]$', i) is not None)

Output:

True
False
False

Working code demo

edited May 03 '17 at 07:43

answered May 03 '17 at 07:21

Chankey Pathak

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What if I want to not have [?.!] appear anywhere else in the string, but only at the end. – Ludisposed May 03 '17 at 07:34
Then also the above regex will work fine. Check the regex demo link and try your test string there. – Chankey Pathak May 03 '17 at 07:35
But it won't allow "," or ";" or quotes inside the sentence, either. – lenz May 03 '17 at 08:14
@lenz Yes that is why I posted an awnser myself and updated the question. – Ludisposed May 03 '17 at 08:42

score 1 · Answer 3 · answered May 03 '17 at 07:21

1

Your regex checks for a single digit in the range [A-Z]. You should change to something like:

^[A-Z].*[?.!]$

Change the .* to whatever you want to match between the capital letter and the punctuation at the end of the string.

answered May 03 '17 at 07:21

Maroun

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`.*` must always be avoided. – Chankey Pathak May 03 '17 at 07:22

Python regex to match punctuation at end of string

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