How to parse a number from line

Question

I have a text file as follows and am trying to create a new text file. There is number on each string with a parenthesis. I need some help on how to parse this number.

test.txt

itemA (3)     
itemB (test) abcd (2)    
itemC xyx (3)

output.txt file to be created as:

itemA-1  
itemA-2  
itemA-3  
itemB (test) abcd-1  
itemB (test) abcd-2  
itemC xyx-1  
itemC xyx-2   
itemC xyx-3

My current code:

import os  
f = open('C:\\Dropbox\\test.txt','r')  
data = f.read()  
print (data)  
f.close()

To format code for stackoverflow, just paste it in verbatim and press Ctrl+K. Thanks! — phihag
– phihag, Commented Sep 6, 2012 at 19:58

Martijn Pieters · Accepted Answer · 2012-09-06 20:11:58Z

Easy enough with a regular expression:

r'\s*\((\d+)\)'

That'll match (optional) whitespace, followed by a number in parethesis, with the number put in a group for easy replacing:

parensnumber = re.compile(r'\s*\((\d+)\)')

count = int(parensnumber.search(line).group(1))
for i in range(count):
    print(parensnumber.sub('-{0}'.format(i + 1), line))

Demo:

>>> import re
>>> parensnumber = re.compile(r'\s*\((\d+)\)')
>>> parensnumber.sub(r'-\1', 'itemA (3)')
'itemA-3'
>>> parensnumber.sub(r'-\1',  'itemB (test) abcd (2)')
'itemB (test) abcd-2'
>>> line = 'itemB (test) abcd (2)'
>>> count = int(parensnumber.search(line).group(1))
>>> for i in range(count):
...     print(parensnumber.sub('-{0}'.format(i + 1), line))
... 
itemB (test) abcd-1
itemB (test) abcd-2

Complete code for your specific example:

import os
import re

parensnumber = re.compile(r'\s*\((\d+)\)')

with open('C:\\Dropbox\\test.txt','r') as input:
    for line in input:
        count = int(parensnumber.search(line).group(1))
        for i in range(count):
            print(parensnumber.sub('-{0}'.format(i + 1), line))

Pablo Santa Cruz · Accepted Answer · 2012-09-06 19:59:14Z

1

Try this:

o = open('output.txt', 'w')
for line in open('text.txt'):
    vals = line.split(' ')
    n = int(vals[-1][1:-1])
    for i in range(n):
        o.write("%s-%d" % (" ".join(vals[:-1]), i))
o.close()

Provided your INPUT is correct. Although you might want to consider using REGEXPs instead of parsing it "by hand".

answered Sep 6, 2012 at 19:59

Pablo Santa Cruz

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