Python threading.Condition 源码解析：从底层锁机制到 wait/notify 流程

import threading


# 条件变量,用于复杂的线程间同步锁
"""
需求:
  男:小姐姐,你好呀!
  女:哼,想泡老娘不成?
  男:对呀,想泡你
  女:滚蛋,门都没有!
  男:切,长这么丑, 还这么吊...
  女:关你鸟事!

"""
class Boy(threading.Thread):
  def __init__(self, name, condition):
    super().__init__(name=name)
    self.condition = condition

  def run(self):
    with self.condition:
      print("{}:小姐姐,你好呀!".format(self.name))
      self.condition.wait()
      self.condition.notify()

      print("{}:对呀,想泡你".format(self.name))
      self.condition.wait()
      self.condition.notify()

      print("{}:切,长这么丑, 还这么吊...".format(self.name))
      self.condition.wait()
      self.condition.notify()


class Girl(threading.Thread):
  def __init__(self, name, condition):
    super().__init__(name=name)
    self.condition = condition

  def run(self):
    with self.condition:
      print("{}:哼,想泡老娘不成?".format(self.name))
      self.condition.notify()
      self.condition.wait()

      print("{}:滚蛋,门都没有!".format(self.name))
      self.condition.notify()
      self.condition.wait()

      print("{}:关你鸟事!".format(self.name))
      self.condition.notify()
      self.condition.wait()


if __name__ == '__main__':
  condition = threading.Condition()
  boy_thread = Boy('男', condition)
  girl_thread = Girl('女', condition)

  boy_thread.start()
  girl_thread.start()

 def __enter__(self):
    return self._lock.__enter__()

  def __exit__(self, *args):
    return self._lock.__exit__(*args)

 def __exit__(self, t, v, tb):
    self.release()

def release(self):
    """Release a lock, decrementing the recursion level.

    If after the decrement it is zero, reset the lock to unlocked (not owned
    by any thread), and if any other threads are blocked waiting for the
    lock to become unlocked, allow exactly one of them to proceed. If after
    the decrement the recursion level is still nonzero, the lock remains
    locked and owned by the calling thread.

    Only call this method when the calling thread owns the lock. A
    RuntimeError is raised if this method is called when the lock is
    unlocked.

    There is no return value.

    """
    if self._owner != get_ident():
      raise RuntimeError("cannot release un-acquired lock")
    self._count = count = self._count - 1
    if not count:
      self._owner = None
      self._block.release()

all_waiters = self._waiters  
waiters_to_notify = _deque(_islice(all_waiters, n))# 从_waiters中取出n个
if not waiters_to_notify:  # 如果是None,结束
   return
for waiter in waiters_to_notify: # 循环release
   waiter.release()
   try:
     all_waiters.remove(waiter) #从_waiters中移除
   except ValueError:
     pass