Locking a file in Python

Question

I need to lock a file for writing in Python. It will be accessed from multiple Python processes at once. I have found some solutions online, but most fail for my purposes as they are often only Unix based or Windows based.

Answer 1

Update as of June 2024

Nowadays there seem to be a number of robust, cross-platform, actively-maintained solutions to this. A few of the most cited in other answers and comments are:

• filelock
• Portalocker
• oslo.concurrency (if you need more general multi-process synchronization utilities)

Original Answer

Alright, so I ended up going with the code I wrote here, on my website ^{link is dead, view on archive.org} (also available on GitHub). I can use it in the following fashion:

from filelock import FileLock

with FileLock("myfile.txt.lock"):
    # work with the file as it is now locked
    print("Lock acquired.")