cs.threads 20190923

threading and communication/synchronisation conveniences

Latest release 20190923: Remove dependence on cs.obj.

Thread related convenience classes and functions.

Class AdjustableSemaphore

A semaphore whose value may be tuned after instantiation.

Function bg(func, daemon=None, name=None, no_start=False, no_logexc=False, args=None, kwargs=None)

Dispatch the callable func in its own Thread; return the Thread.

Parameters:

• func: a callable for the Thread target.
• daemon: optional argument specifying the .daemon attribute.
• name: optional argument specifying the Thread name, default: the name of func.
• no_start: optional argument, default False. If true, do not start the Thread.
• no_logexc: if false (default False), wrap func in @logexc.
• args, kwargs: passed to the Thread constructor

Class LockableMixin

Trite mixin to control access to an object via its ._lock attribute. Exposes the ._lock as the property .lock. Presents a context manager interface for obtaining an object's lock.

Function locked(func)

A decorator for monitor functions that must run within a lock. Relies upon a ._lock attribute for locking.

Function locked_property(func, lock_name='_lock', prop_name=None, unset_object=None)

A thread safe property whose value is cached. The lock is taken if the value needs to computed.

Class PriorityLock

A priority based mutex.

A priority based mutex which is acquired by and released to waiters in priority order.

The initialiser sets a default priority, itself defaulting to 0.

The acquire() method accepts an optional priority value which specifies the priority of the acquire request; lower values have higher priorities. acquire returns a new PriorityLockSubLock.

Note that internally this allocates a threading.Lock per acquirer.

When acquire is called, if the PriorityLockis taken then the acquirer blocks on their personalLock`.

When release() is called the highest priority Lock is released.

Within a priority level acquires are served in FIFO order.

Used as a context manager, the mutex is obtained at the default priority.

The priority() method offers a context manager with a specified priority.

Method PriorityLock.__init__(self, default_priority=0, name=None)

Initialise the PriorityLock.

Parameters:

• default_priority: the default acquire priority, default 0.
• name: optional identifying name

Function via(cmanager, func, *a, **kw)

Return a callable that calls the supplied func inside a with statement using the context manager cmanager. This intended use case is aimed at deferred function calls.

Class WorkerThreadPool

MRO: cs.resources.MultiOpenMixin
A pool of worker threads to run functions.

Method WorkerThreadPool.__init__(self, name=None, max_spare=4)

Initialise the WorkerThreadPool.

Parameters:

• name: optional name for the pool
• max_spare: maximum size of each idle pool (daemon and non-daemon)

Class WTPoolEntry

MRO: builtins.tuple
WTPoolEntry(thread, queue)

Release Log

Release 20190923: Remove dependence on cs.obj.

Release 20190921: New PriorityLock class for a mutex which releases in (priority,fifo) order.

Release 20190812: bg: compute default name before wrapping func in @logexc.

Release 20190729: bg: provide default name, run callable inside Pfx, add optional no_logexc=False param preventing @logec wrapper if true.

Release 20190422: bg(): new optional no_start=False keyword argument, preventing Thread.start if true

Release 20190102: Drop some unused classes. New LockableMixin, presenting a context manager and a .lock property.

Release 20160828: Use "install_requires" instead of "requires" in DISTINFO.

Release 20160827: Replace bare "excepts" with "except BaseException". Doc updates. Other minor improvements.

Release 20150115: First PyPI release.