How do I search for a pattern within a text file using Python combining regex & string/file operations and store instances of the pattern?

import repattern = re.compile("<(\d{4,5})>")for i, line in enumerate(open('test.txt')):    for match in re.finditer(pattern, line):        print 'Found on line %s: %s' % (i+1, match.group())

A couple of notes about the regex:

• You don't need the ? at the end and the outer (...) if you don't want to match the number with the angle brackets, but only want the number itself
• It matches either 4 or 5 digits between the angle brackets

Update: It's important to understand that the match and capture in a regex can be quite different. The regex in my snippet above matches the pattern with angle brackets, but I ask to capture only the internal number, without the angle brackets.

More about regex in python can be found here : Regular Expression HOWTO

Doing it in one bulk read:

import retextfile = open(filename, 'r')filetext = textfile.read()textfile.close()matches = re.findall("(<(\d{4,5})>)?", filetext)

Line by line:

import retextfile = open(filename, 'r')matches = []reg = re.compile("(<(\d{4,5})>)?")for line in textfile:    matches += reg.findall(line)textfile.close()

But again, the matches that returns will not be useful for anything except counting unless you added an offset counter:

import retextfile = open(filename, 'r')matches = []offset = 0reg = re.compile("(<(\d{4,5})>)?")for line in textfile:    matches += [(reg.findall(line),offset)]    offset += len(line)textfile.close()

But it still just makes more sense to read the whole file in at once.