我想知道Python中是否有用于异步方法调用的库。如果你能做点什么就太好了
@async
def longComputation():
<code>
token = longComputation()
token.registerCallback(callback_function)
# alternative, polling
while not token.finished():
doSomethingElse()
if token.finished():
result = token.result()
或者异步调用非异步例程
def longComputation()
<code>
token = asynccall(longComputation())
如果在语言核心中有一个更精细的策略就太好了。考虑过这个问题吗?
当前回答
Just
import threading, time
def f():
print "f started"
time.sleep(3)
print "f finished"
threading.Thread(target=f).start()
其他回答
你可以使用eventlet。它允许您编写看似同步的代码，但却可以在网络上异步操作。
下面是一个超级小爬虫的例子:
urls = ["http://www.google.com/intl/en_ALL/images/logo.gif",
"https://wiki.secondlife.com/w/images/secondlife.jpg",
"http://us.i1.yimg.com/us.yimg.com/i/ww/beta/y3.gif"]
import eventlet
from eventlet.green import urllib2
def fetch(url):
return urllib2.urlopen(url).read()
pool = eventlet.GreenPool()
for body in pool.imap(fetch, urls):
print "got body", len(body)
这对我来说很有用，你可以调用这个函数，它会把自己分派到一个新的线程上。
from thread import start_new_thread
def dowork(asynchronous=True):
if asynchronous:
args = (False)
start_new_thread(dowork,args) #Call itself on a new thread.
else:
while True:
#do something...
time.sleep(60) #sleep for a minute
return
从Python 3.5开始，可以对异步函数使用增强的生成器。
import asyncio
import datetime
增强的生成器语法:
@asyncio.coroutine
def display_date(loop):
end_time = loop.time() + 5.0
while True:
print(datetime.datetime.now())
if (loop.time() + 1.0) >= end_time:
break
yield from asyncio.sleep(1)
loop = asyncio.get_event_loop()
# Blocking call which returns when the display_date() coroutine is done
loop.run_until_complete(display_date(loop))
loop.close()
新的async/await语法:
async def display_date(loop):
end_time = loop.time() + 5.0
while True:
print(datetime.datetime.now())
if (loop.time() + 1.0) >= end_time:
break
await asyncio.sleep(1)
loop = asyncio.get_event_loop()
# Blocking call which returns when the display_date() coroutine is done
loop.run_until_complete(display_date(loop))
loop.close()
我的解决方案是:
import threading
class TimeoutError(RuntimeError):
pass
class AsyncCall(object):
def __init__(self, fnc, callback = None):
self.Callable = fnc
self.Callback = callback
def __call__(self, *args, **kwargs):
self.Thread = threading.Thread(target = self.run, name = self.Callable.__name__, args = args, kwargs = kwargs)
self.Thread.start()
return self
def wait(self, timeout = None):
self.Thread.join(timeout)
if self.Thread.isAlive():
raise TimeoutError()
else:
return self.Result
def run(self, *args, **kwargs):
self.Result = self.Callable(*args, **kwargs)
if self.Callback:
self.Callback(self.Result)
class AsyncMethod(object):
def __init__(self, fnc, callback=None):
self.Callable = fnc
self.Callback = callback
def __call__(self, *args, **kwargs):
return AsyncCall(self.Callable, self.Callback)(*args, **kwargs)
def Async(fnc = None, callback = None):
if fnc == None:
def AddAsyncCallback(fnc):
return AsyncMethod(fnc, callback)
return AddAsyncCallback
else:
return AsyncMethod(fnc, callback)
并完全按要求工作:
@Async
def fnc():
pass
它不在语言核心中，但Twisted是一个非常成熟的库，可以做你想要的事情。它引入Deferred对象，您可以将回调或错误处理程序(“errbacks”)附加到该对象。Deferred基本上是一个“承诺”，即一个函数最终会有一个结果。
