来自tornado.gen documentation可以有人帮我理解tornado.gen.coroutine和tornado.gen.engine之间的确切区别
最佳答案
正如gen.engine的龙卷风文档所说:
This decorator is similar to coroutine,except it does not return a
Future and the callback argument is not treated specially.
正如gen.coroutine文档所说
From the caller’s perspective,@gen.coroutine is similar to the
combination of @return_future and @gen.engine.
gen.engine基本上是一个比coroutine更老的,更简化的版本.如果您正在编写新代码,则应遵循文档的建议并始终使用tornado.gen.coroutine.
发动机:
def engine(func): @functools.wraps(func) def wrapper(*args,**kwargs): runner = None def handle_exception(typ,value,tb): if runner is not None: return runner.handle_exception(typ,tb) return False with ExceptionStackContext(handle_exception) as deactivate: try: result = func(*args,**kwargs) except (Return,StopIteration) as e: result = getattr(e,'value',None) else: if isinstance(result,types.GeneratorType): def final_callback(value): if value is not None: raise ReturnValueIgnoredError( "@gen.engine functions cannot return values: " "%r" % (value,)) assert value is None deactivate() runner = Runner(result,final_callback) runner.run() return if result is not None: raise ReturnValueIgnoredError( "@gen.engine functions cannot return values: %r" % (result,)) deactivate() # no yield,so we're done return wrapper
@H_404_34@协程:
def coroutine(func): @functools.wraps(func) def wrapper(*args,**kwargs): runner = None future = TracebackFuture() if 'callback' in kwargs: callback = kwargs.pop('callback') IOLoop.current().add_future( future,lambda future: callback(future.result())) def handle_exception(typ,tb): try: if runner is not None and runner.handle_exception(typ,tb): return True except Exception: typ,tb = sys.exc_info() future.set_exc_info((typ,tb)) return True with ExceptionStackContext(handle_exception) as deactivate: try: result = func(*args,None) except Exception: deactivate() future.set_exc_info(sys.exc_info()) return future else: if isinstance(result,types.GeneratorType): def final_callback(value): deactivate() future.set_result(value) runner = Runner(result,final_callback) runner.run() return future deactivate() future.set_result(result) return future return wrapper
@H_404_34@乍一看,这些都可能很难理解.但是,显然代码非常相似,除了@ gen.coroutine对回调kwarg有一些特殊的处理,它构建/返回一个Future. @ gen.engine有一些代码,如果你试图从它返回一些东西,而不是把它放在Future中,它会特意抛出一个错误.