Allow a simple way to ensure execution is confined to one thread.
This module defines the Affinity data type that runs code on a single thread. An instance of the class will execute functions only on the thread that made the object in the first place. The class is useful in a GUI's main loop.
Python, 79 lines
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This module defines the Affinity data type that runs code on a single thread.
An instance of the class will execute functions only on the thread that made
the object in the first place. The class is useful in a GUI's main loop."""
__author__ = 'Stephen "Zero" Chappell <Noctis.Skytower@gmail.com>'
__date__ = '4 June 2012'
__version__ = 1, 0, 0
################################################################################
import sys
import _thread
import queue
################################################################################
def slots(names=''):
"Sets the __slots__ variable in the calling context with private names."
sys._getframe(1).f_locals['__slots__'] = \
tuple('__' + name for name in names.replace(',', ' ').split())
################################################################################
class Affinity:
"Affinity() -> Affinity instance"
slots('thread, action')
def __init__(self):
"Initializes instance with thread identity and job queue."
self.__thread = _thread.get_ident()
self.__action = queue.Queue()
def __call__(self, func, *args, **kwargs):
"Executes function on creating thread and returns result."
if _thread.get_ident() == self.__thread:
while not self.__action.empty():
self.__action.get_nowait()()
return func(*args, **kwargs)
delegate = _Delegate(func, args, kwargs)
self.__action.put_nowait(delegate)
return delegate.value
################################################################################
class _Delegate:
"_Delegate(func, args, kwargs) -> _Delegate instance"
slots('func, args, kwargs, mutex, value, error')
def __init__(self, func, args, kwargs):
"Initializes instance from arguments and prepares to run."
self.__func = func
self.__args = args
self.__kwargs = kwargs
self.__mutex = _thread.allocate_lock()
self.__mutex.acquire()
def __call__(self):
"Executes code with arguments and allows value retrieval."
try:
self.__value = self.__func(*self.__args, **self.__kwargs)
self.__error = False
except:
self.__value = sys.exc_info()[1]
self.__error = True
self.__mutex.release()
@property
def value(self):
"Waits for value availability and raises or returns data."
self.__mutex.acquire()
if self.__error:
raise self.__value
return self.__value
|
This module is utilized by threadbox (recipe 578152) to clone classes so their instances execute on a single thread. Directory Pruner 4 (recipe 578154) also takes advantage of the provided slots function.
Tags: cpu_usage, threadsafe
