Find one file out of many containing a desired string in Python

Question

I have a string like 'apples'. I want to find this string, and I know that it exists in one out of hundreds of files. e.g.

file1
file2
file3
file4
file5
file6
...
file200

All of these files are in the same directory. What is the best way to find which file contains this string using python, knowing that exactly one file contains it.

I have come up with this:

for file in os.listdir(directory):
    f = open(file)
    for line in f:
        if 'apple' in f:
            print "FOUND"
    f.close()

and this:

grep = subprocess.Popen(['grep','-m1','apple',directory+'/file*'],stdout=subprocess.PIPE)
found = grep.communicate()[0]
print found

Are all of these files in the same directory?

Levon
– Levon

2012-06-22 19:16:46 +00:00
Commented Jun 22, 2012 at 19:16 — Levon
– Levon, Commented Jun 22, 2012 at 19:16

Levon · Accepted Answer · 2012-06-22 19:54:57Z

11

Given that the files are all in the same directory, we just get a current directory listing.

import os

for fname in os.listdir('.'):    # change directory as needed
    if os.path.isfile(fname):    # make sure it's a file, not a directory entry
        with open(fname) as f:   # open file
            for line in f:       # process line by line
                if 'apples' in line:    # search for string
                    print 'found string in file %s' %fname
                    break

This automatically gets the current directory listing, and checks to make sure that any given entry is a file (not a directory).

It then opens the file and reads it line by line (to avoid problems with memory it doesn't read it in all at once) and looks for the target string in each line.

When it finds the target string it prints the name of the file.

Also, since the files are opened using with they are also automatically closed when we are done (or an exception occurs).

edited Jun 22, 2012 at 19:54

answered Jun 22, 2012 at 19:22

Levon

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7 Comments

Ashwini Chaudhary Over a year ago

os.listdir('.') returns both files and folder.

E.Cross Over a year ago

My solution is very similar except that I close the file manually. And I am absolutely positive that nothing else in that folder is every going to be there except those files, since they are generated by another program. Are you saying this is the fastest way?

Levon Over a year ago

@AshwiniChaudhary Yes, that's true

Levon Over a year ago

@Dan .. so you won't ever have directories to worry about? I think in terms of writing this in Python only, I can't think of a faster way. Whether creating a subprocess to spawn grep will be faster will probably depend on how many files you are searching. The overhead for this will diminish in relation to the number of files. To know for sure would be to time it.

Levon Over a year ago

@Dan One difference is that your code won't close files in case of an exception. As you aren't worried about directories, that difference is not significant in your case, but that check ordinarily would be a good idea to have.

|

ninjagecko · Accepted Answer · 2012-06-22 19:24:54Z

2

For simplicity, this assumes your files are in the current directory:

def whichFile(query):
    for root,dirs,files in os.walk('.'):
        for file in files:
            with open(file) as f:
                if query in f.read():
                    return file

answered Jun 22, 2012 at 19:24

ninjagecko

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Comments

Ben · Accepted Answer · 2012-06-22 19:24:54Z

2

for x in  os.listdir(path):
    with open(x) as f:
        if 'Apple' in f.read():
         #your work
        break

answered Jun 22, 2012 at 19:24

Ben

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Comments

iruvar · Accepted Answer · 2012-06-22 20:26:45Z

0

a lazy-evaluation, itertools-based approach

import os
from itertools import repeat, izip, chain

gen = (file for file in os.listdir("."))
gen = (file for file in gen if os.path.isfile(file) and os.access(file, os.R_OK))
gen = (izip(repeat(file), open(file)) for file in gen)
gen = chain.from_iterable(gen)
gen = (file for file, line in gen if "apple" in line)
gen = set(gen)
for file in gen:
  print file

answered Jun 22, 2012 at 20:26

iruvar

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Comments

Aurelie Giraud · Accepted Answer · 2021-12-07 11:54:06Z

0

Open your terminal and write this:

Case insensitive search

grep -i 'apple' /path/to/files

Recursive search (through all sub folders)

grep -r 'apple' /path/to/files

answered Dec 7, 2021 at 11:54

Aurelie Giraud

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