file accessing in python

Question

i searched for the answer couldn't get it.

i have the following code,

filePointer = open(r'c:\temp\logFile.txt', 'w')
filePointer.write(str( datetime.datetime.now()) + 'entered into table \n' )

but before i enter the above line into file, i want to check if it is already present in it. i can read the file and string compare and all, but I'm looking for a better way, help me out if there is any.

perhaps [this SO post](http://stackoverflow.com/questions/4940032/search-for-string-in-txt-file-python) answers your question? — zehnpaard, Feb 17 '15 at 06:56
Your question is rather unclear. As you open the file in `w` mode it will be truncated and will only contain the added line. And anyway, it will only contain the line if it was previously added in same second. Please clarify what you need. — Serge Ballesta, Feb 17 '15 at 06:56
yeah, i want to check if it is previously added in a loop, if the string is added already, i dont want to add it again. — Shrinidhi Kanchi, Feb 17 '15 at 07:00
zehnpaard, the same. i wanted to know if there is any command or one line function to check for the purpose — Shrinidhi Kanchi, Feb 17 '15 at 07:01
@ Ignacio Vazquez-Abrams i'm looking if 'entered into table' string is previously added or not. — Shrinidhi Kanchi, Feb 17 '15 at 07:03

score 0 · Accepted Answer · answered Feb 17 '15 at 07:21

Shrinidhi,

I believe this what you're looking for. First you need to not use 'w' on open since that will cause any new writing to the file to replace the current contents. Instead you should use 'a' or 'a+' to append to the file. See code below:

from datetime import datetime

line_to_add = 'def'

with open('file.txt', 'a+') as openfile:
    if not (item for item in openfile if line_to_add not in line):
        openfile.write(str(datetime.now()) + " " + line_to_add + ' \n')

This will check if the line is already in the file. If it's not there it will add it with a time stamp.

You'll have to string compare, but at lease it's using a generator to do so.

file accessing in python

1 Answers1