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

Answer 1

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

Answer 2

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