How to input a regex in string.replace?

Question

I need some help on declaring a regex. My inputs are like the following:

this is a paragraph with<[1> in between</[1> and then there are cases ... where the<[99> number ranges from 1-100</[99>.  and there are many other lines in the txt files with<[3> such tags </[3> 

The required output is:

this is a paragraph with in between and then there are cases ... where the number ranges from 1-100.  and there are many other lines in the txt files with such tags 

I've tried this:

#!/usr/bin/python import os, sys, re, glob for infile in glob.glob(os.path.join(os.getcwd(), '*.txt')):     for line in reader:          line2 = line.replace('<[1> ', '')         line = line2.replace('</[1> ', '')         line2 = line.replace('<[1>', '')         line = line2.replace('</[1>', '')                  print line 

I've also tried this (but it seems like I'm using the wrong regex syntax):

        line2 = line.replace('<[*> ', '')         line = line2.replace('</[*> ', '')         line2 = line.replace('<[*>', '')         line = line2.replace('</[*>', '') 

I dont want to hard-code the replace from 1 to 99.

Answer 1

This tested snippet should do it:

import re line = re.sub(r"</?\[\d+>", "", line) 

Edit: Here's a commented version explaining how it works:

line = re.sub(r"""   (?x) # Use free-spacing mode.   <    # Match a literal '<'   /?   # Optionally match a '/'   \[   # Match a literal '['   \d+  # Match one or more digits   >    # Match a literal '>'   """, "", line) 

Regexes are fun! But I would strongly recommend spending an hour or two studying the basics. For starters, you need to learn which characters are special: "metacharacters" which need to be escaped (i.e. with a backslash placed in front - and the rules are different inside and outside character classes.) There is an excellent online tutorial at: www.regular-expressions.info. The time you spend there will pay for itself many times over. Happy regexing!

Answer 2

str.replace() does fixed replacements. Use re.sub() instead.