7.2.2.threading

1.Introduction
- This module constructs higher-level threading interfaces on top of the lower level thread module. See also the mutex and Queue modules.

2.Usage

創建Thread的方式有兩種:
- 1.創建一個類別並覆寫Threading.Thread:
  - 在此類別中的init()中傳入參數, 此參數通常是要讓thread執行的function, 呼叫super.init()
  - 覆寫run(), 通常在這裡執行傳入的function
- 2.直接呼叫Threading.Thread

比較好的架構如下:

-ThreadRunner-

最上層的包裝, Thread的管理者:
- 私有變數中有一個Thread pool, 可以是list或是dictionary
- 提供addThreadWorker(), 以添加Thread(Worker)到Thread pool
- 提供run(), 以啟動Thread pool中所有的Thread(Worker)

class TheradRunner():
  def __init__(self):
      self.__threadPool = {}

  def addThreadWorker(self, worker, name):
      self.__threadPool.update({name:Thread(worker)})

  def run(self):
      for name, thread in self.__threadPool.items():
          thread.start()
      for name, thread in self.__threadPool.items():
          thread.join()

-Thread-

繼承threading.Thread
- 在init()中傳入Worker, 在這裡可以用hasattr檢查woker的run()是否是callable, 並用hasattr檢查worker的run是否存在
- 在init()中呼叫super.init()
- 覆寫run(), 通常在這裡執行傳入的function

class Thread(threading.Thread):
  def __init__(self, workerClass):
      super().__init__()
      self.status = Status.Init
      if hasattr(workerClass, 'run') and callable(workerClass.run):
          self.__workerClass = workerClass
          self.exceptionMessage = None
      else:
          self.status = Status.Error
          self.exceptionMessage = 'Worker function error'

  def start(self):
      if Status.Init == self.status:
           self.status = Status.Running
           super().start()

 def run(self):
      try:
          self.__workerClass.run()
          self.status = Status.Success
      except Exception:
          self.exceptionMessage = traceback.format_exc()
          self.status = Status.Error

-Worker-

提供run(), 真正要讓Thread作的事
若有很多不同的事情分別要讓不同的thread執行, 則可以分別撰寫不同類別, 這些類別都需要繼承Worker

class Worker():
  def run(self):
      pass

class ReadLineWorker(Worker):
  def __init__(self, aHoldingZoneMap):
      self.__holdingZoneTableMap = aHoldingZoneMap

  def run(self):
      self.readLinesAndAttribute()

-製作新的thread-

lineWorker = ReadLineWorker(holdingZoneTableMap)
threadRunner.addThreadWorker(lineWorker, 'ReadLineWorker')
threadRunner.run()

3.Reference

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class TheradRunner(): def __init__(self): self.__threadPool = {} def addThreadWorker(self, worker, name): self.__threadPool.update({name:Thread(worker)}) def run(self): for name, thread in self.__threadPool.items(): thread.start() for name, thread in self.__threadPool.items(): thread.join()

class Thread(threading.Thread): def __init__(self, workerClass): super().__init__() self.status = Status.Init if hasattr(workerClass, 'run') and callable(workerClass.run): self.__workerClass = workerClass self.exceptionMessage = None else: self.status = Status.Error self.exceptionMessage = 'Worker function error' def start(self): if Status.Init == self.status: self.status = Status.Running super().start() def run(self): try: self.__workerClass.run() self.status = Status.Success except Exception: self.exceptionMessage = traceback.format_exc() self.status = Status.Error