What's wrong with my regex to extract time from a string?

Question

I'm trying to come up with a regex to extract time out of a string to build an application.

Here's what I've got so far. Not sure what am I doing wrong here.

I can get some the string but not all of the different variations.

([01]?[0-9]*:?[0-9]*[AP]M?)-([01]?[0-9]*:?[0-9]*[AP]M?)


8-8:30AM MON TUES THURS FRI
8-10:30AM MON TUES THURS FRI
8:30AM-10:30AM MON TUES THURS FRI
10:30AM-11:30AM MON TUES THURS FRI
10:30AM-11:30AM MON TUES THURS FRI
8AM-8:30AM
10-11PM

What I want is two captured groups. So I know that the first group is FROM time and the later one is TO time.

vks · Accepted Answer · 2015-12-22 19:18:45Z

5

([01]?[0-9]+:?[0-9]*(?:[AP]M)?)-([01]?[0-9]+:?[0-9]*(?:[AP]M)?)
           ^^               ^^            ^^                 ^^

Just make AM component optional.See demo.Also make first part + or else it will match empty strings.

https://regex101.com/r/fC0lI5/2

edited Dec 22, 2015 at 19:18

answered Dec 22, 2015 at 19:13

vks

68.1k11 gold badges96 silver badges132 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Tyler Sebastian Over a year ago

yours will match 10M-12M, which doesn't make sense

Mr. E Over a year ago

This matches 10:30A-10:31M

Mr. E Over a year ago

[AP]?M? should be instead (?:[AP]M)?

Patrick Fournier Over a year ago

This matches a lot more than needed: 3782328328-23 for example

Tyler Sebastian · Accepted Answer · 2015-12-22 19:22:30Z

5

The AM/PM in either capture group is not optional

([01]?[0-9]+:?[0-9]*(?:[AP]M)?)-([01]?[0-9]+:?[0-9]*(?:[AP]M)?)

I think mine is more valid than the others because the others will allow (they've since fixed theirs)

8M-9M, which is not valid.

edited Dec 22, 2015 at 19:22

answered Dec 22, 2015 at 19:14

Tyler Sebastian

9,5887 gold badges42 silver badges64 bronze badges

Comments

Patrick Fournier · Accepted Answer · 2015-12-22 19:41:05Z

2

As pointed by other answers, the A and P are not optional. Furthermore, your regex will match other strings (like ":A-:A" or "98387899A-A").

This works and will be stricter that yours:

((?:[01]?[0-9]:)?[0-9]{1,2}(?:AM|PM)?)-((?:[01]?[0-9]:)?[0-9]{1,2}(?:AM|PM)?)

See the Python manual for a complete description of the regex syntax.

edited Dec 22, 2015 at 19:41

answered Dec 22, 2015 at 19:26

Patrick Fournier

6887 silver badges20 bronze badges

1 Comment

vks Over a year ago

We actually cannot use regex to validate time ...it would be tough....like this will match 0-0.nonetheless plus one

Collectives™ on Stack Overflow

What's wrong with my regex to extract time from a string?

3 Answers 3

4 Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related