Python threads file lock

This file locking-unlocking dance has been extracted into a decorator. Instead of using a operating system feature, programs can negotiate their own system for signalling when a file is in use. They use lock sometimes called shadow files. Vim does this. So does Emacs. The lock object supports multiple ways for acquiring the lock, including the ones used to acquire standard Python thread locks:.

The acquire method accepts also a timeout parameter. If the lock cannot be acquired within timeout seconds, a Timeout exception is raised:. The lock objects are recursive locks, which means that once acquired, they will not block on successive lock requests:. Use the FileLock if all instances of your application are running on the same host and a SoftFileLock otherwise. The SoftFileLock only watches the existence of the lock file.

Hi tylerneylon , thank you for the clear explanation. I learned a lot. I wonder about other options in realizing this task. Thanks for the idea.

Hi IceflowRE — If a read lock is active, then the write lock cannot be acquired until that read lock is complete. In that case, it is incorrect usage of this class. I am not trying to protect against bad usage of the class — only to support correct usage of it.

The same philosophy is true of many concurrency tools. Hi nidhimad , there is not really an ownership between readers and the write lock. Instead, the write lock is locked when either there is a writer, and there can only be one writer or there are any readers, and there can be many simultaneous readers. This has interesting overlap between the readers, but we don't actually care about the order -- we only care that the write lock is held until all readers are done.

So this is the sequence of events in the example:. Skip to content. Sign in Sign up. Instantly share code, notes, and snippets.

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