current community

your communities

more stack exchange communities

company blog
Stack Exchange Inbox Reputation and Badges
tour help
stack overflow careers
Sign up ×
Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them, it only takes a minute:
up vote 53 down vote favorite
13

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 . . .

share|improve this question
2  
The accepted answer already covers your problem and solves it. Do you need anything else ? – HamZa Jun 25 '13 at 14:02
1  
not really, just getting more attention to the question =) – alvas Jun 25 '13 at 14:08
    
What should be the result for where the<[99> number ranges from 1-100</[100>? – utapyngo Jun 26 '13 at 5:19
    
it should also remove the number in the <...> tag, so the output should be where the number rangers from 1-100 ? – alvas Jun 26 '13 at 6:12

6 Answers 6

up vote 113 down vote accepted
+150

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!

share|improve this answer
    
care to explain the regex? – alvas Apr 14 '11 at 6:35
    
yep it works!! thanks but can you explain the regex in brief? – alvas Apr 14 '11 at 6:39
3  
Also don't neglect The Book on Regular Expressions - Mastering Regular Expressions, by Jeffrey Friedl – pcurry May 14 '13 at 5:05
    
@pcurry - I agree 110% - Most useful book I've ever read. – ridgerunner May 14 '13 at 5:48
up vote 15 down vote

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

share|improve this answer
2  
Also worth noting that your pattern should look something like "</{0-1}\d{1-2}>" or whatever variant of regexp notation python uses. – bdares Apr 14 '11 at 4:05
    
What does fixed replacements mean? – avi Jul 3 at 11:35
up vote 1 down vote

don't have to use regular expression (for your sample string)

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

>>> for w in s.split(">"):
...   if "<" in w:
...      print w.split("<")[0]
...
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
share|improve this answer
up vote 6 down vote

The easiest way

import re

txt='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>'

out = re.sub("(<[^>]+>)", '', txt)
print out
share|improve this answer
up vote 2 down vote

replace method of string objects does not accept regular expressions but only fixed strings (see documentation: http://docs.python.org/2/library/stdtypes.html#str.replace).

You have to use re module:

import re
newline= re.sub("<\/?\[[0-9]+>", "", line)
share|improve this answer
up vote 3 down vote

I would go like this (regex explained in comments):

import re

# If you need to use the regex more than once it is suggested to compile it.
pattern = re.compile(r"</{0,}\[\d+>")

# <\/{0,}\[\d+>
# 
# Match the character “<” literally «<»
# Match the character “/” literally «\/{0,}»
#    Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «{0,}»
# Match the character “[” literally «\[»
# Match a single digit 0..9 «\d+»
#    Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
# Match the character “>” literally «>»

subject = """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>"""

result = pattern.sub("", subject)

print(result)

If you want to learn more about regex I recomend to read Regular Expressions Cookbook by Jan Goyvaerts and Steven Levithan.

share|improve this answer
    
You could simply use * instead of {0,} – HamZa Jun 27 '13 at 10:39
1  
I think that {0,} is more readable. Just a matter of style – Boydon Jun 27 '13 at 11:31

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.