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I've tried to read a txt file and find the lines which contain a certain word "checkout_revision". I want to find these lines one by one in a for loop and store them in my variable, let say temp. I heard grep with cut is suitable for this. However I could not do that. Is there anyone to help me? Here is my code :

for line in intersect:
        cmd=""" grep "CHECKOUT_REVISION" |cut -d\'\"\' -f2"""%fst_directory
share|improve this question
Why do this in bash? You'd rather open the file in python (or whatever language you are using) and do this operation there. – panmari Aug 23 '13 at 15:35
Yea , Why I couldnt have been think that lol – caesar Aug 23 '13 at 15:37

Suppose there is a file /home/eday/test.txt with the contents bellow:

this is a test

another line

CHECKOUT_REVISION this must be stored

some other things
CHECKOUT_REVISION another line to store

The following Python script will read the file stored in my_file variable looking for what is stored in look_for variable and if it finds a match, it will store it in temp variable which is a list variable.

Finally it will print to the output the contents of temp You can comment out or delete the printing line.

#!/usr/bin/env python

# path to the file to read from
my_file = "/home/eday/test.txt"
# what to look in each line
# variable to store lines containing CHECKOUT_REVISION
temp = []

with open(my_file, "r") as file_to_read:
    for line in file_to_read:
        if look_for in line:

# print the contents of temp variable
print (temp)

the above script will have the following output in terminal:

$ ['CHECKOUT_REVISION this must be stored', 'CHECKOUT_REVISION another line to store']
share|improve this answer
result = []
for line in open('filename'):
    if 'CHECKOUT_REVISION' in line:

I suppose this is what you want - you get a list of strings with second field of each line which contain string CHECKOUT_REVISION. The question should be moved to stackoverflow though.

share|improve this answer
I want to search on a file . – caesar Aug 23 '13 at 16:51
@Eday well okay, if intersect is not a variable holding strings, then you go with for line in open('filename'):. It is quite simple and there's really no need for external tools, if you only check if a substring is present and then split line into records. – moon.musick Aug 23 '13 at 17:17

Inspired from above answers, here is command line version.

#!/usr/bin/env python

import sys

pattern = sys.argv[1]
fileName = sys.argv[2]

temp = []

with open(fileName, "r") as file_to_read:
    for line in file_to_read:
        if pattern in line:
           #IN case you want to have number of hits

for i in range(count):
    print (temp[i].rstrip())

Run it like:

python "pattern" 
share|improve this answer

I agree that Stef's answer is a good answer, but if you still want to use grep or cut (or others) commands from bash in python, I suggest you do not use os.system, but to use subprocess module. For example:

#!/usr/bin/env python

import subprocess

cmd = "grep CHECKOUT_REVISION /home/eday/test.txt | cut -d'\"' -f2 -s"
process = subprocess.Popen(cmd, stdout=subprocess.PIPE, shell=True)
temp = process.communicate()[0]

print (temp)

If /home/eday/test.txt file is something like this:

some lines
CHECKOUT_REVISION="revision one"
some other lines
CHECKOUT_REVISION="revision two"
other lines

the output of the above python script will be:

revision one
revision two
share|improve this answer
@radu-rdeanu why dont use os.system / – caesar Aug 24 '13 at 12:06
@Eday Using subprocess module you can control the stdout. os.system is deprecated. See – Radu Rădeanu Aug 24 '13 at 12:25

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