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
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
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)
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。
喜欢的东西:
import threading
thr = threading.Thread(target=foo, args=(), kwargs={})
thr.start() # Will run "foo"
....
thr.is_alive() # Will return whether foo is running currently
....
thr.join() # Will wait till "foo" is done
有关详细信息，请参阅https://docs.python.org/library/threading.html上的文档。
Just
import threading, time
def f():
print "f started"
time.sleep(3)
print "f finished"
threading.Thread(target=f).start()
你可以使用并发。期货(在Python 3.2中添加)。
import time
from concurrent.futures import ThreadPoolExecutor
def long_computation(duration):
for x in range(0, duration):
print(x)
time.sleep(1)
return duration * 2
print('Use polling')
with ThreadPoolExecutor(max_workers=1) as executor:
future = executor.submit(long_computation, 5)
while not future.done():
print('waiting...')
time.sleep(0.5)
print(future.result())
print('Use callback')
executor = ThreadPoolExecutor(max_workers=1)
future = executor.submit(long_computation, 5)
future.add_done_callback(lambda f: print(f.result()))
print('waiting for callback')
executor.shutdown(False) # non-blocking
print('shutdown invoked')
