defer.py 文件源码

def _startRunCallbacks(self, result):
        if self.called:
            if self._suppressAlreadyCalled:
                self._suppressAlreadyCalled = False
                return
            if self.debug:
                if self._debugInfo is None:
                    self._debugInfo = DebugInfo()
                extra = "\n" + self._debugInfo._getDebugTracebacks()
                raise AlreadyCalledError(extra)
            raise AlreadyCalledError
        if self.debug:
            if self._debugInfo is None:
                self._debugInfo = DebugInfo()
            self._debugInfo.invoker = traceback.format_stack()[:-2]
        self.called = True
        self.result = result
        self._runCallbacks()