How to apply Condition in regex

Question

Hello i am a newbie and currently trying to learn about regex pattern by experimenting on various patterns. I tried to create the regex pattern for this url but failed. It's a pagination link of amazon.

http://www.amazon.in/s/lp_6563520031_pg_2?rh=n%3A5866078031%2Cn%3A%215866079031%2Cn%3A6563520031&page=2s&ie=UTF8&qid=1446802571

Or

http://www.amazon.in/Tena-Wet-Wipe-Pulls-White/dp/B001O1G242/ref=sr_1_46?s=industrial&ie=UTF8&qid=1446802608&sr=1-46

I just want to check the url by only these two things.

If the url has dp directory or product directory

If the url has query string page having any digit

I tried to create the regex pattern but failed. I want that if the first thing is not there the regex pattern should match the second (or vice versa).

Here's the regex pattern I made:

.*\/(dp|product)\/ | .*page

Here is my regex101 link: https://regex101.com/r/zD2gP5/1#python

Could you explain about these **three languages** tags? javascript or php or python? — Remi Guan, Nov 06 '15 at 10:19
@KevinGuan Oh sorry, i thought that the people there maybe knowing about regex. Should i remove them? — Utkarsh Dixit, Nov 06 '15 at 10:19
If you want to check only,why matching the whole input? Just check with [`\/(?:dp|product)\/|[&?]page=`](https://regex101.com/r/uQ8xZ9/1). — Wiktor Stribiżew, Nov 06 '15 at 10:21
But there is *little* difference between their regex, are you using php regex? — Remi Guan, Nov 06 '15 at 10:21
@KevinGuan Actually i am using python but i thought the regex would work same for different languages. My fault.... — Utkarsh Dixit, Nov 06 '15 at 10:22
@stribizhev Can you post this as an answer. I wanted this one — Utkarsh Dixit, Nov 06 '15 at 10:23
Well, take a look at [this question](http://stackoverflow.com/questions/4644847/list-of-all-regex-implementations) :) — Remi Guan, Nov 06 '15 at 10:29

Wiktor Stribiżew · Accepted Answer · 2015-11-06T10:26:12.263

Since you just want to check if a string contains some pattern, you can use

\/(?:dp|product)\/|[&?]page=

See regex demo

In Python, just check with re.search:

import re
p = re.compile(r'/(?:dp|product)/|[&?]page=')
test_str = "http://w...content-available-to-author-only...n.in/s/lp_6563520031_pg_2?rh=n%3A5866078031%2Cn%3A%215866079031%2Cn%3A6563520031&page=2s&ie=UTF8&qid=14468025716"
if p.search(test_str):
    print ("Found!")

Also, in Python regex patterns, there is no need to escape / slashes.

The regex matches two alternative subpatterns (\/(?:dp|product)\/ and [&?]page=):

/ - a forward slash
(?:dp|product) - either dp or product (without storing the capture inside the capture buffer since it is a non-capturing group)
/ - a slash
| - or...
[&?] - either a & or ? (we check the start of a query string parameter)
page= - literal sequence of symbols page=.

score 2 · Answer 2 · edited Nov 06 '15 at 12:55

2

\/(dp|product)\/|page=(?=[^&]*\d)[^&]+

This would be my idea, please test it and let me know if you have question about.

edited Nov 06 '15 at 12:55

Utkarsh Dixit

4,267
3
15
38

answered Nov 06 '15 at 12:15

zolo

444
2
6

Try to run this one regex101.com . Your previous query /(dp|product)/|page=(?=[^&]*\d)[^&]+. You just forget to escape the slashes. But Thanks – Utkarsh Dixit Dec 25 '15 at 17:50

How to apply Condition in regex

2 Answers2