gen.py 文件源码

def handle_yield(self, yielded):
        # Lists containing YieldPoints require stack contexts;
        # other lists are handled in convert_yielded.
        if _contains_yieldpoint(yielded):
            yielded = multi(yielded)

        if isinstance(yielded, YieldPoint):
            # YieldPoints are too closely coupled to the Runner to go
            # through the generic convert_yielded mechanism.
            self.future = TracebackFuture()

            def start_yield_point():
                try:
                    yielded.start(self)
                    if yielded.is_ready():
                        self.future.set_result(
                            yielded.get_result())
                    else:
                        self.yield_point = yielded
                except Exception:
                    self.future = TracebackFuture()
                    self.future.set_exc_info(sys.exc_info())

            if self.stack_context_deactivate is None:
                # Start a stack context if this is the first
                # YieldPoint we've seen.
                with stack_context.ExceptionStackContext(
                        self.handle_exception) as deactivate:
                    self.stack_context_deactivate = deactivate

                    def cb():
                        start_yield_point()
                        self.run()
                    self.io_loop.add_callback(cb)
                    return False
            else:
                start_yield_point()
        else:
            try:
                self.future = convert_yielded(yielded)
            except BadYieldError:
                self.future = TracebackFuture()
                self.future.set_exc_info(sys.exc_info())

        if not self.future.done() or self.future is moment:
            self.io_loop.add_future(
                self.future, lambda f: self.run())
            return False
        return True