Python regular expression syntax

Python regular expression syntax … here is a solution to the problem.

I’m a beginner in python regular expressions. So can someone help me understand the following syntax?

r'^(? P<pk>\d+)/results/$'

I came across this statement while learning Django.

Expression decomposition:

^ : matches the beginning of the string
(? P<pk>\d+): Matches 1 or more numbers (0-9) and captures them as a named group PK
/results/ : matches the text /results/
$ : matches at the end of the string.

So a URL path that starts with a number followed by the text /results/ match:

1234/results/
42/results/
3/results/

But nothing else.

If used in a Django url configuration, the number is captured and passed as pk to the keyword parameter in the attached View.