Package: portalocker
OverviewPortalocker is a library to provide an easy API to file locking.An important detail to note is that on Linux and Unix systems the locks are
advisory by default. By specifying the-o mandoption to the mount command it
is possible to enable mandatory file locking on Linux. This is generally not
recommended however. For more information about the subject:https://en.wikipedia.org/wiki/File_lockinghttp://stackoverflow.com/questions/39292051/portalocker-does-not-seem-to-lockhttps://stackoverflow.com/questions/12062466/mandatory-file-lock-on-linuxThe module is currently maintained by Rick van Hattem <Wolph@wol.ph>.
The project resides athttps://github.com/WoLpH/portalocker. Bugs and feature
requests can be submitted there. Patches are also very welcome.Security contact informationTo report a security vulnerability, please use theTidelift security contact.
Tidelift will coordinate the fix and disclosure.Redis LocksThis library now features a lock based on Redis which allows for locks across
multiple threads, processes and even distributed locks across multiple
computers.It is an extremely reliable Redis lock that is based on pubsub.As opposed to most Redis locking systems based on key/value pairs,
this locking method is based on the pubsub system. The big advantage is
that if the connection gets killed due to network issues, crashing
processes or otherwise, it will still immediately unlock instead of
waiting for a lock timeout.First make sure you have everything installed correctly:pip install "portalocker[redis]"Usage is really easy:import portalocker

lock = portalocker.RedisLock('some_lock_channel_name')

with lock:
    print('do something here')The API is essentially identical to the otherLockclasses so in addition
to thewithstatement you can also uselock.acquire(...).Python 2Python 2 was supported in versions before Portalocker 2.0. If you are still
using
Python 2,
you can run this to install:pip install "portalocker<2"TipsOn some networked filesystems it might be needed to force aos.fsync()before
closing the file so it’s actually written before another client reads the file.
Effectively this comes down to:with portalocker.Lock('some_file', 'rb+', timeout=60) as fh:
    # do what you need to do
    ...

    # flush and sync to filesystem
    fh.flush()
    os.fsync(fh.fileno())LinksDocumentationhttp://portalocker.readthedocs.org/en/latest/Sourcehttps://github.com/WoLpH/portalockerBug reportshttps://github.com/WoLpH/portalocker/issuesPackage homepagehttps://pypi.python.org/pypi/portalockerMy bloghttp://w.wol.ph/ExamplesTo make sure your cache generation scripts don’t race, use theLockclass:>>> import portalocker
>>> with portalocker.Lock('somefile', timeout=1) as fh:
...     print('writing some stuff to my cache...', file=fh)To customize the opening and locking a manual approach is also possible:>>> import portalocker
>>> file = open('somefile', 'r+')
>>> portalocker.lock(file, portalocker.LockFlags.EXCLUSIVE)
>>> file.seek(12)
>>> file.write('foo')
>>> file.close()Explicitly unlocking is not needed in most cases but omitting it has been known
to cause issues:https://github.com/AzureAD/microsoft-authentication-extensions-for-python/issues/42#issuecomment-601108266If needed, it can be done through:>>> portalocker.unlock(file)Do note that your data might still be in a buffer so it is possible that your
data is not available until youflush()orclose().To create a cross platform bounded semaphore across multiple processes you can
use theBoundedSemaphoreclass which functions somewhat similar tothreading.BoundedSemaphore:>>> import portalocker
>>> n = 2
>>> timeout = 0.1>>> semaphore_a = portalocker.BoundedSemaphore(n, timeout=timeout)
>>> semaphore_b = portalocker.BoundedSemaphore(n, timeout=timeout)
>>> semaphore_c = portalocker.BoundedSemaphore(n, timeout=timeout)>>> semaphore_a.acquire()
<portalocker.utils.Lock object at ...>
>>> semaphore_b.acquire()
<portalocker.utils.Lock object at ...>
>>> semaphore_c.acquire()
Traceback (most recent call last):
  ...
portalocker.exceptions.AlreadyLockedMore examples can be found in thetests.VersioningThis library followsSemantic Versioning.ChangelogEvery release has agit tagwith a commit message for the tag
explaining what was added and/or changed. The list of tags/releases
including the commit messages can be found here:https://github.com/WoLpH/portalocker/releasesLicenseSee theLICENSEfile.