python regular expression search not finding underscore in path

I have a long file which follows some structure and I want to parse this file to extract an object called sample:

The file named paths_text.txt is like that:

/groups/cgsd/javed/validation_set/LeungSY_Targeted_SS-190528-01a/Clean/pfg001G_1_Clean.fastq.gz  /groups/cgsd/javed/validation_set/LeungSY_Targeted_SS-190528-01a/Clean/pfg001G_2_Clean.fastq.gz  /groups/cgsd/javed/validation_set/LeungSY_Targeted_SS-190528-01a/Clean/pfg001T_1_Clean.fastq.gz  /groups/cgsd/javed/validation_set/LeungSY_Targeted_SS-190528-01a/Clean/pfg001T_2_Clean.fastq.gz  

My code runs fine like this:

import os  os.chdir('/groups/cgsd/alexandre/python_code')  import re      with open('./src/paths_text.txt') as f:      for line in f:          sample = re.search(r'pfg\d+',line)          print(sample)  

But when I search for underscore I get None as a result of my match, why?

import os  os.chdir('/groups/cgsd/alexandre/python_code')  import re      with open('./src/paths_text.txt') as f:      for line in f:          sample = re.search(r'pfg\d+_',line)          print(sample)  

https://stackoverflow.com/questions/65912347/python-regular-expression-search-not-finding-underscore-in-path January 27, 2021 at 11:05AM