python subprocess is overwriting file used for stdout - I need it to append to the file (windows)

Question

I want to append the `STDOUT` of `subprocess.call()` to an existing file. My code below overwrites the file - ``` log_file = open(log_file_path, 'r+') cmd = r'echo "some info for the log file"' subprocess.call(cmd, shell=True, stdout=log_file, stderr=STDOUT) log_file.close() ``` I'm looking for the equivalent of `>>` in `subprocess.call()` or `subprocess.Popen()`. It's driving me crazy trying to find it.. UPDATE: Following the answers so far I've updated my code to ``` import subprocess log_file = open('test_log_file.log', 'a+') cmd = r'echo "some info for the log file
"' subprocess.call(cmd, shell=True, stdout=log_file, stderr=subprocess.STDOUT) log_file.close() ``` I'm running this code from the command line in windows - ``` C:\users\aidan>test_subprocess.py ``` This adds the text to the log file. When I run the script again, nothing new is added. It still seems to be overwriting the file..

Accepted Answer

Use the 'a' append mode instead:

```
log_file = open(log_file_path, 'a+')
```

If you still see previous content overwritten, perhaps Windows needs you to explicitly seek to the end of the file; open as 'r+' or 'w' and seek to the end of the file:

```
import os

log_file = open(log_file_path, 'r+')
log_file.seek(0, os.SEEK_END)
```

python subprocess is overwriting file used for stdout - I need it to append to the file (windows)

Solution

Problem