python - 异步协程

Question

我以为我已经和 David Beazley 的协程搞清楚了，非常好 presentation但我无法将其与 PEP-492 中描述的新语法完全协调。 。

在演讲中，他解释了如何将协程视为一条管道，它被推送到而不是像生成器中那样被拉出。

例如:

# cofollow.py
#
# A simple example showing how to hook up a pipeline with
# coroutines.   To run this, you will need a log file.
# Run the program logsim.py in the background to get a data
# source.

from coroutine import coroutine

# A data source.  This is not a coroutine, but it sends
# data into one (target)

import time
def follow(thefile, target):
    thefile.seek(0,2)      # Go to the end of the file
    while True:
         line = thefile.readline()
         if not line:
             time.sleep(0.1)    # Sleep briefly
             continue
         target.send(line)

# A sink.  A coroutine that receives data

@coroutine
def printer():
    while True:
         line = (yield)
         print line,

# Example use
if __name__ == '__main__':
    f = open("access-log")
    follow(f,printer())

如何使用这一新语法实现 printer() 协程？我还没有看到协程被推送到使用这种新语法的示例。可能吗？

Answer 1

你所拥有的并不是 asyncio 模块和/或 PEP-492 意义上的协程。正如 PEP 本身所说:

[This PEP] is relevant only to the kind of coroutine that uses yield as a signal to the scheduler, indicating that the coroutine will be waiting until an event (such as IO) is completed.

1. 您的示例中不涉及调度程序(事件循环)，并且
2. 协程不使用 yield 仅“作为调度程序的信号”；它实际上是用它来读取数据。