[SOLVED] Python modifies a closed file at program exit

jlinkels · 08-23-2018, 08:08 PM

I am trying to modify the time stamp of a file used in python.

Before running the script, I have this:

Code:

jlinkels@donald-pc:/tmp$ echo "Hello World" > /tmp/filter_cc.log
jlinkels@donald-pc:/tmp$ stat filter_cc.log
Access: 2018-08-24 00:56:05.942539951 +0000
Modify: 2018-08-24 00:56:05.942539951 +0000
Change: 2018-08-24 00:56:05.942539951 +0000

That is fine. Then I run this Python script:

Code:

#! /usr/bin/python

import os, sys

os.utime ("/tmp/filter_cc.log", (1394628000.0,1394628000.0))
sys.exit()

After exiting the script I run stat again:

Code:

jlinkels@donald-pc:/tmp$ stat filter_cc.log
Access: 2018-08-24 00:58:10.441487778 +0000
Modify: 2014-03-12 12:40:00.000000000 +0000
Change: 2018-08-24 00:58:09.941491078 +0000

That is OK. The time stamp in the os.utime statement is a date in 2014.

Now this is the problem: When I access the file in the Python script, it is modified after the os.utime statement. Presumably at exit. Before running the script I delete the previous file.
So this is the script:

Code:

#! /usr/bin/python

import os, sys

logfile = open ('/tmp/filter_cc.log', 'w')
logfile.write ("Hello world\n")
logfile.close 

os.utime ("/tmp/filter_cc.log", (1394628000.0,1394628000.0))
sys.exit()

So I would expect that the os.utime call would set the file time to 2014. Just like in the first script. However, this is what happens:

Code:

jlinkels@donald-pc:/tmp$ stat filter_cc.log
Access: 2018-08-24 01:03:36.042778408 +0000
Modify: 2018-08-24 01:03:35.542783334 +0000
Change: 2018-08-24 01:03:35.542783334 +0000

And that is definitely not good. The last statement is the script is a os.utime. But it seems Python modifies the closed file once more on the OS level.

Running Debian Jessie, Python 2.7.9

jlinkels

jlinkels · 08-23-2018, 08:44 PM

Solved. The file was not closed at all.

Code:

logfile.close

instead of

Code:

logfile.close()

jlinkels

dugan · 08-23-2018, 09:59 PM

The pattern to use is:

Code:

with open ('/tmp/filter_cc.log', 'w') as logfile:
    logfile.write ("Hello world\n")

That ensures that the file is closed no matter what.

jlinkels · 08-24-2018, 07:32 AM

I just started in Python. I think I am still too much used to old school, open(), write() and close(). And also the expectation that Python would generate an error when stating close instead of close(). I have "some" programming experience, back to Algol 60 and Fortran IV, so this assumptions might work against me. Never mind, one is never too old to learn.

jlinkels