How do I watch a file for changes?


I have a log file being written by another process which I want to watch for changes. Each time a change occurs I'd like to read the new data in to do some processing on it.

What's the best way to do this? I was hoping there'd be some sort of hook from the PyWin32 library. I've found the win32file.FindNextChangeNotification function but have no idea how to ask it to watch a specific file.

If anyone's done anything like this I'd be really grateful to hear how...

[Edit] I should have mentioned that I was after a solution that doesn't require polling.

[Edit] Curses! It seems this doesn't work over a mapped network drive. I'm guessing windows doesn't 'hear' any updates to the file the way it does on a local disk.

4/7/2017 1:43:23 AM

Accepted Answer

Have you already looked at the documentation available on If you only need it to work under Windows the 2nd example seems to be exactly what you want (if you exchange the path of the directory with the one of the file you want to watch).

Otherwise, polling will probably be the only really platform-independent option.

Note: I haven't tried any of these solutions.

10/8/2008 11:43:17 AM

Did you try using Watchdog?

Python API library and shell utilities to monitor file system events.

Directory monitoring made easy with

  • A cross-platform API.
  • A shell tool to run commands in response to directory changes.

Get started quickly with a simple example in Quickstart...

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