Why does my file get overwritten?

Question

When using this code in python:

 f = open('ping.log', 'r+')
 f.write("["+time.ctime()+"]"+"Status")
 f.close()

My file always gets overwritten. And only has one line in it, like this:

[Fri Sep 02 16:30:56 2011]Status

Why is it getting overwritten?

Is what you're trying to say something like: "I am using Python 2.7 on Windows XP. I do two file writes: {CODE SAMPLE} Why is the file only showing the first write, but not the second?" Because that code sample's important. — deworde, Aug 30 '11 at 13:41
Code: f = open('ping.log', 'r+') f.write("["+time.ctime()+"]"+"Status") f.close() — Zygimantas, Aug 30 '11 at 13:43
You remember to tell `f` you want to _append_ to its current contents? — Thorbjørn Ravn Andersen, Aug 30 '11 at 13:54

ChrisF · Accepted Answer · 2011-08-30T14:12:59.453

5

It's failing because you are effectively recreating the file each time as you are overwriting the first N bytes every time. If you wrote less bytes you'd see the "old" information still there.

You need to open the file for "append"

'a' opens the file for appending

Source

edited Aug 30 '11 at 14:12

answered Aug 30 '11 at 14:03

ChrisF

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Not recreating, it just overwrites the first N bytes. It'd be visible if there was more content inside it. – Cat Plus Plus Aug 30 '11 at 14:06

score 2 · Answer 2 · answered Aug 30 '11 at 14:03

2

r+ sets the initial file pointer to the beginning. Either seek to the end or use a mode.

answered Aug 30 '11 at 14:03

Cat Plus Plus

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score 2 · Answer 3 · edited May 23 '17 at 12:12

2

Check this question. Open the file with the "a" mode:

f = open("ping.log","a")
...

edited May 23 '17 at 12:12

Community

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answered Aug 30 '11 at 14:04

Geo

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score 2 · Answer 4 · answered Aug 30 '11 at 14:07

http://docs.python.org/tutorial/inputoutput.html#reading-and-writing-files

The first argument is a string containing the filename. The second argument is another string containing a few characters describing the way in which the file will be used. mode can be 'r' when the file will only be read, 'w' for only writing (an existing file with the same name will be erased), and 'a' opens the file for appending; any data written to the file is automatically added to the end. 'r+' opens the file for both reading and writing. The mode argument is optional; 'r' will be assumed if it’s omitted.

so use

f = open('ping.log', 'a')
f.write("["+time.ctime()+"]"+"Status")
f.close()

Why does my file get overwritten?

4 Answers4