Python not closing file descriptors

Question

I am developing a long-running python script which makes many connections to different serial ports. The script crashes a few hours into its execution citing "Too many open files". I have tracked the issue to the serial module where the .close() method does not seem to reduce the number of file descriptors python is using. I am checking this using `lsof | grep python | wc`. Using Debian 7.2 & Python 2.7.3 The example below slowly uses up more and more file descriptors until it hits the limit. Why is this and how can I avoid it?? ``` #!/usr/bin/env python import serial #Used to communicate with pressure controller import logging import time from time import gmtime, strftime logging.basicConfig(filename="open_files_test.log") # Write unusual + significant events to logfile + stdout def log( message ): time = strftime("%Y-%m-%d %H:%M:%S", gmtime()) logging.warning( time + " " + message ) print( message ) for i in range(2000): for n in range(1, 12): try: port_name = "/dev/tty" + str(n+20)…

Accepted Answer

It seems that extra `com.open` is causing the issue. According to the docs `serial.Serial` returns it open, so you don't need to open it once more. In Linux (all POSIXes as far as I know) `open` just increments the counter and close just decrements it. There is a deleted answer here by @wheaties advising using `with` which I would recommend as well:

```
with serial.Serial(port_name, 9600, ...) as com:
    com.flushInput()
    com.flushOutput()
    ...
```

Python not closing file descriptors

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