where to find detailed description and working examples of Python regular expressions?

Question

[natasha.sernova]

Dear all!

I know Python regexps were taken from Perl, but in my opinion they lost a lot in this transition.

So far I've found several "theoretical" examples of Python regular expression application.

There are a few ways to search for them, like 'match' or 'findall' depending on the final goal.

This is not enough for me, I need your advice where to find more information with short script examples?

Many-many thanks!

Natasha

Example of my unsuccessul trials with SwissProt file:

import re
import random
import math
import sys
print "This is the name of the script: ", sys.argv[0]
print "Number of arguments: ", len(sys.argv)
print "The arguments are: " , str(sys.argv)

#if m:
#print 'Match found: ', m.group()
#else:
#print 'No match' 

fin = open(sys.argv[1], 'r')
for line in fin:
    a = re.match(r'^AC', line)
    if a is not None:
        a.group
    a = re.match(r'^DE', line)
    if a is not None:
        a.group
    a = re.match(r'^OC', line)
    if a is not None:
        a.group
    a = re.match(r'^KW', line) 
    if a is not None:
        a.group
    a = re.match(r'(^SQ).+(\d+\s+\w{2})', line)
    if a is not None:
        a.group 
#        print "\1"+"\s"+"\2"
    re.sub(r'[\s,\n]','', line) 
    print line
    a = re.match(r'^//', line) 
    if a is not None:   
        break
fin.close()

I've got the whole initial SwissProt-file,

[Medhat]

beside documentation of course, that could help you

http://www.diveintopython3.net/regular-expressions.html
https://pymotw.com/2/re/

and for example you can test by yourself here

[natasha.sernova]

That's perfect! Thousand thanks! I've never seen anything similar - usually a few lines and that's it.

[Medhat]

Note: It is better performance to use

with open("yourfile", "r"):
        # do something

# instead of

myfile =  open("yourfile", "r")

[natasha.sernova]

Thank you very much again! I've realized that I write regexps from Perl in Python...