Check if a file is modified in Python

Question

I am trying to create a box that tells me if a file text is modified or not, if it is modified it prints out the new text inside of it. This should be in an infinite loop (the bot sleeps until the text file is modified).

I have tried this code but it doesn't work.

while True:
    tfile1 = open("most_recent_follower.txt", "r")
    SMRF1 = tfile1.readline()
    if tfile1.readline() == SMRF1:
        print(tfile1.readline())

But this is totally not working... I am new to Python, can anyone help me?

By "modified" you meant added new line?

heemayl
– heemayl

2015-01-21 00:01:45 +00:00
Commented Jan 21, 2015 at 0:01 — heemayl
– heemayl, Commented Jan 21, 2015 at 0:01

settwi · Accepted Answer · 2022-11-19 04:40:52Z

5

This is the first result on Google for "check if a file is modified in python" so I'm gonna add an extra solution here.

If you're curious if a file is modified in the sense that its contents have changed, OR it was touched, then you can use os.stat:

import os
get_time = lambda f: os.stat(f).st_ctime

fn = 'file.name'
prev_time = get_time(fn)

while True:
    t = get_time(fn)
    if t != prev_time:
        do_stuff()
        prev_time = t

answered Nov 19, 2022 at 4:40

settwi

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Comments

jgritty · Accepted Answer · 2015-01-21 00:14:09Z

2

def read_file():
    with open("most_recent_follower.txt", "r") as f:
        SMRF1 = f.readlines()
    return SMRF1

initial = read_file()
while True:
    current = read_file()
    if initial != current:
        for line in current:
            if line not in initial:
                print(line)
        initial = current

Read the file in once, to get it's initial state. Then continuously repeat reading of the file. When it changes, print out its contents.

I don't know what bot you are referring to, but this code, and yours, will continuously read the file. It never seems to exit.

edited Jan 21, 2015 at 0:14

answered Jan 21, 2015 at 0:03

jgritty

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5 Comments

heemayl Over a year ago

OP wants only the new next entered if the file is modified, not the whole file contents.

Speedy Boosting Over a year ago

I have just tried your code, the problem is that it keeps printint "current" for ever, how can I fix this?

jgritty Over a year ago

It shouldn't ever print "current", but I updated it to only print new lines added to the file.

Speedy Boosting Over a year ago

Tried it again, it still loops printing the new value inside the text file :S

jgritty Over a year ago

That last line should fix it.

ThorSummoner · Accepted Answer · 2015-01-21 00:31:18Z

0

I might suggest copying the file to a safe duplicate location, and possibly using a diff program to determine if the current file is different from the original copy, and print the added lines. If you just want lines appended you might try to utilize a utility like tail

You can also use a library like pyinotify to only trigger when the filesystem detects the file has been modified

edited Jan 21, 2015 at 0:31

answered Jan 21, 2015 at 0:21

ThorSummoner

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1 Comment

Speedy Boosting Over a year ago

Thanks for the reply, but I tried jgritty code and it works as I desired! Thanks anyway :)

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