code: def acquire(self, blocking=1):
          
          rc = False
          with self.__cond:
              while self.__value == 0:
                  if not blocking:
                      break
                  if __debug__:
                      self._note("%s.acquire(%s): blocked waiting, value=%s",
                              self, blocking, self.__value)
                  self.__cond.wait()
              else:
                  self.__value = self.__value - 1
                  if __debug__:
                      self._note("%s.acquire: success, value=%s",
                              self, self.__value)
                  rc = True
          return rc
docs: Acquire a semaphore, decrementing the internal counter by one.
  
          When invoked without arguments: if the internal counter is larger than
          zero on entry, decrement it by one and return immediately. If it is zero
          on entry, block, waiting until some other thread has called release() to
          make it larger than zero. This is done with proper interlocking so that
          if multiple acquire() calls are blocked, release() will wake exactly one
          of them up. The implementation may pick one at random, so the order in
          which blocked threads are awakened should not be relied on. There is no
          return value in this case.
  
          When invoked with blocking set to true, do the same thing as when called
          without arguments, and return true.
  
          When invoked with blocking set to false, do not block. If a call without
          an argument would block, return false immediately; otherwise, do the
          same thing as when called without arguments, and return true.