问题描述
由tornado.gen 有人可以帮助我了解tornado.gen之间准确的区别.coroutine和tornado.gen.engine
Going by the tornado.gen documentation can someone help me understand the exact difference between tornado.gen.coroutine and tornado.gen.engine
推荐答案
由于龙卷风文档 gen.engine 说：
这装饰类似于协程，但它不返回
未来和回调参数没有经过特殊处理。
和作为 gen.coroutine 文件说
从呼叫者的角度来看，@ gen.coroutine类似于
@return_future和@ gen.engine的组合。
gen.engine 基本上是协同程序做什么的老，少精简版。如果你正在编写新的code，你应该遵循的文件的意见，并总是用 tornado.gen.coroutine 。
gen.engine is basically an older, less streamlined version of what coroutine does. If you're writing new code, you should follow the documentation's advice and always use tornado.gen.coroutine.
如果你看一下code这两个功能（与剥离出来的文档）这是pretty明显。
It's pretty evident if you look at the code for both functions (with documentation stripped out).
引擎：
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, value, 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
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, value, tb):
try:
if runner is not None and runner.handle_exception(typ, value, tb):
return True
except Exception:
typ, value, tb = sys.exc_info()
future.set_exc_info((typ, value, tb))
return True
with ExceptionStackContext(handle_exception) as deactivate:
try:
result = func(*args, **kwargs)
except (Return, StopIteration) as e:
result = getattr(e, 'value', 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
这两个可能是pretty很难第一眼就明白了。但尽管如此，很明显，在code非常相似，不同的是 @ gen.coroutine 的回调的一些特殊的处理 kwarg，和它建立/返回未来。 @ gen.engine 有一些code，如果你试图从它返回的东西，而不是把它在未来专门抛出一个错误。
Both of these are probably pretty hard to understand at first glance. But still, it's obvious that the code is very similar, except that @gen.coroutine has some special handling of the callback kwarg, and it builds/returns a Future. @gen.engine has some code that specifically throws an error if you try to return something from it, rather than putting it in the Future.
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