python: search file for string

Question

I have tried to create a python function which takes in 2 parameters; a file name and a search string. In this case the file name is the script itself (script.py) and the search string is 'name = "JOHN"'

#!/usr/local/bin/python2.7

import os, sys

#################
# Variable string
name = "JOHN"

#################
# Main function
def search_script_for_string(filename, searchString):

f = open(filename,'r') #open the given filename then
filedata = f.read()    #assign it to variable then
f.close()              #close the open filename

for lines in filedata:        #loop through each line in the filedata variable
    if searchString in lines: #if search string is found, then do all of this
        print ('Found string: %s') % searchString
        return True

    else:           #if not found, then do all of this
        print ('Did not find: %s') % searchString
        return False
        break

#################
# Pass the file name and the search string parameter to the function

search_script_for_string("test.py","name = \"" + name + "\"")

The problem is that it doesn't return expected results:

$ Did not find: name = "JOHN"

When it meant to say:

$ Found string: name = "JOHN"

If anyone can help correct my understanding of where I'm going wrong here, I'd be massively appreciative. Thanks

mgilson · Accepted Answer · 2016-03-02 14:37:43Z

2

f.read() returns the entire contents of the file as a single string. You then iterate over those contents -- but iterating over a string yields only 1 character at a time so there is no way a character will contain the substring you are looking for.

def search_script_for_string(filename, searchString):
    with open(filename, 'r') as f:
        return searchString in f.read()

should do the trick. Alternatively, if you want to search line-by-line:

def search_script_for_string(filename, searchString):
    with open(filename, 'r') as f:
        for line in f:
            return searchString in line

answered Mar 2, 2016 at 14:37

mgilson

312k70 gold badges656 silver badges722 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

mgilson Over a year ago

Note, I've used a context manager for managing the opening and closing of the file. You could continue to open and close the file as you have above, but the context manager is just a bit nicer IMHO :-)

stackoflow Over a year ago

Great response in a speedy 2 mins! Thank you.

DevShark · Accepted Answer · 2016-03-02 14:40:05Z

0

You are iterating over each character of the file by calling for c in f.read().

Use for line in f and you will indeed iterate over each line.

Also prefer the use of with, this makes your code a lot more robust.

So this would be better:

with open('fileName') as f:
    for line in f:
        #process

answered Mar 2, 2016 at 14:40

DevShark

9,18810 gold badges36 silver badges68 bronze badges

Collectives™ on Stack Overflow

python: search file for string

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related