locket 0.2.1

File-based locks for Python for Linux and Windows

Locket implements a lock that can be used by multiple processes provided they use the same path.

import locket

# Wait for lock
with locket.lock_file("path/to/lock/file"):
    perform_action()

# Raise error if lock cannot be acquired immediately
with locket.lock_file("path/to/lock/file", timeout=0):
    perform_action()

# Raise error if lock cannot be acquired after thirty seconds
with locket.lock_file("path/to/lock/file", timeout=30):
    perform_action()

# Without context managers:
lock = locket.lock_file("path/to/lock/file")
try:
    lock.acquire()
    perform_action()
finally:
    lock.release()

Locks largely behave as (non-reentrant) Lock instances from the threading module in the standard library. Specifically, their behaviour is:

• Locks are uniquely identified by the file being locked, both in the same process and across different processes.

• Locks are either in a locked or unlocked state.

• When the lock is unlocked, calling acquire() returns immediately and changes the lock state to locked.

• When the lock is locked, calling acquire() will block until the lock state changes to unlocked, or until the timeout expires.

• If a process holds a lock, any thread in that process can call release() to change the state to unlocked.

• Behaviour of locks after fork is undefined.

Installation

pip install locket