Matching a String in Python using regex

Question

I have a string say like this:

  ARAN22 SKY BYT and TRO_PAN

In the above string The first alphabet can be A or S or T or N and the two numbers after RAN can be any two digit. However the rest will be always same and last three characters will be always like _PAN.

So the few possibilities of the string are :

  SRAN22 SK BYT and TRO_PAN
  TRAN25 SK BYT and TRO_PAN
  NRAN25 SK BYT and TRO_PAN

So I was trying to extract the string every time in python using regex as follows:

import re

pattern =   "([ASTN])RAN" + "\w+\s+" +"_PAN"

pat_check = re.compile(pattern, flags=re.IGNORECASE)

sample_test_string = 'NRAN28 SK BYT and TRO_PAN'

re.match(pat_check, sample_test_string)

here string can be anything like the above examples I gave there.

But its not working as I am not getting the string name ( the sample test string) which I should. Not sure what I am doing wrong. Any help will be very much appreciated.

@Scott I was expecting when I run re.match(pat_check, sample_test_string) , I should be getting the sample-test_string: 'NRAN28 SK BYT and TRO_PAN'. But instead when I run the code, I get None — Stan
– Stan, Commented Oct 12, 2022 at 1:02
pattern = "([ASTN])RAN" + "\w+\s+" +"_PAN" To pick just one example of how the pattern is wrong, it demands that _PAN is immediately preceded by a space, which your sample string clearly does not have. — John Gordon
– John Gordon, Commented Oct 12, 2022 at 1:05
Thanks @JohnGordon I see. Yeah I was trying "([ASTN])RAN" +"\w+" + "\s+" +"TRO_PAN", too, but it fails too as expected and mentioned by you. So then I have to put all the string with spaces for the regex to work? — Stan
– Stan, Commented Oct 12, 2022 at 1:08

Nick · Accepted Answer · 2022-10-12 01:01:47Z

1

You are using \w+\s+, which will match one or more word (0-9A-Za-z_) characters, followed by one or more space characters. So it will match the two digits and space after RAN but then nothing more. Since the next characters are not _PAN, the match will fail. You need to use [\w\s]+ instead:

pattern =   "([ASTN])RAN" + "[\w\s]+" +"_PAN"

answered Oct 12, 2022 at 1:01

Nick

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4 Comments

Stan Over a year ago

oh wonderful. Thats sweet. Thank you @Nick! I learned something new!

Stan Over a year ago

Since you seem to be expert in regex, one more quick help: if my string is like: 'NRAN'28 SK BYT and TRO_PAN' with an apostrophe in between RAN and the number how can I extract that? I was trying "([ASTN])" + + "\'" + "RAN" + "[\w\s]+" +"_PAN". But that does not seem to work. Any ideas ?

Nick Over a year ago

You have the apostrophe in the wrong place in your pattern, it should be after RAN i.e. pattern = "([ASTN])" + "RAN" + "'" + "[\w\s]+" +"_PAN" Note you don't need a backslash before the '.

Stan Over a year ago

oh Nick you are awesome! Thanks for pointing my error. I was continuosly scratching my head!

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