代码示例:
async def download_page(session, url):
print(True)
async def downloader_init(session):
while True:
url = await download_queue.get()
task = asyncio.create_task(download_page(session, url))
print(task)
print(f"url: {url}")
async def get_urls(url):
while True:
try:
url = find_somewhere_url
await download_queue.put(url)
except NoSuchElementException:
break
return True
async def main():
async with aiohttp.ClientSession(headers=headers) as session:
get_urls_task = asyncio.create_task(get_urls(url))
downloader_init_task = asyncio.create_task(downloader_init(session))
asyncio.gather(get_urls_task, downloader_init_task)
if __name__ == "__main__":
asyncio.get_event_loop().run_until_complete(main())
输出:
<Task pending coro=<download_page() running at main.py:69>>
url: https://someurl.com/example
<Task pending coro=<download_page() running at main.py:69>>
url: https://someurl.com/example
<Task pending coro=<download_page() running at main.py:69>>
url: https://someurl.com/example
为什么方法download_page
没有执行?奇怪的是脚本刚刚结束它的工作,任何地方都没有错误。downloader_init
应该无休止地工作,但事实并非如此。
在 中download_queue
,方法在get_urls
找到链接时添加链接,然后停止工作。downloader_init
队列中出现新链接时应立即执行,但仅在get_urls
完成工作后才开始工作。
试试这个:
注意:您的问题不在于任务创建,而是因为该asyncio.gather
部分没有等待。
import asyncio
import aiohttp
async def download_page(session, url):
# Dummy function.
print(f"session={session}, url={url}")
async def downloader_init(session):
while True:
url = await download_queue.get()
task = asyncio.create_task(download_page(session, url))
print(f"task={task}, url={url}")
async def get_urls(url):
while True:
try:
url = find_somewhere_url()
await download_queue.put(url)
except NoSuchElementException:
break
async def main():
async with aiohttp.ClientSession(headers=headers) as session:
get_urls_task = asyncio.create_task(get_urls(url))
downloader_init_task = asyncio.create_task(downloader_init(session))
# Use await here to make it finish the tasks.
await asyncio.gather(get_urls_task, downloader_init_task)
if __name__ == "__main__":
# Use this as it deals with the loop creation, shutdown,
# and other stuff for you.
asyncio.run(main()) # This is new in Python 3.7
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