How to extract particular data in a line using python?

Question

I have a file contains lines like:

754.82915: MODE1(0, 0x001900, 0x00090)
754.82916: MODE2(0, 0x001900, 0x00090)

How to take the data from "(" to ")" in python??.

I tried the code:

fo=open("file1.txt","r")
fin=open("file2.txt","w")
lines=fo.readlines()
for line in lines:
    result=re.search(r'\(.*\)', line)
    res="\n"+result.group()
    fin.write(res)
fo.close()

It showing following error:

AttributeError: 'NoneType' object has no attribute 'group'

That's the exact content of your text file? (May be you've some empty lines as well) — Ashwini Chaudhary
– Ashwini Chaudhary, Commented Jan 14, 2014 at 10:27
re.search(pattern, string, flags=0): Return None if no position in the string matches the pattern; note that this is different from finding a zero-length match at some point in the string. — Grijesh Chauhan
– Grijesh Chauhan, Commented Jan 14, 2014 at 10:28

Ray · Accepted Answer · 2014-01-14 10:42:05Z

1

Sticking to your original code, just add one line to check whether result is None.

with open("file1.txt","r") as fin:
    lines = fin.readlines()
    with open("file2.txt","w") as fout:
        for line in lines:
            result = re.search(r'\(.*\)', line)
            if result:     # check if not None
                res = "\n" + result.group()
                fout.write(res)

You should also learn from @Peter's more pythonic answer.

edited Jan 14, 2014 at 10:42

answered Jan 14, 2014 at 10:35

Ray

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Peter Varo · Accepted Answer · 2014-01-14 10:33:38Z

1

You should consider using the with statements and the findall() function of the re module, like this:

import re

with open('file1.txt', 'r') as fin:
    with open('file2.txt', 'w') as fout:
        fout.write('\n'.join(re.findall(r'\(.*\)', fin.read())))

answered Jan 14, 2014 at 10:33

Peter Varo

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