如下代码中session = None是什么意思?
import asyncio,aiohttp
CONCURRENCY = 5
URL = 'https://www.baidu.com'
semaphore = asyncio.Semaphore(CONCURRENCY)
session = None
async def scrape_api():
async with semaphore:
print('Scraping',URL)
async with session.get(URL) as response:
await asyncio.sleep(1)
return await response.text()
async def main():
global session
session = aiohttp.ClientSession()
scrape_index_tasks = [asyncio.ensure_future(scrape_api()) for _ in range(100)]
await asyncio.gather(*scrape_index_tasks)
if __name__ == '__main__':
asyncio.get_event_loop().run_until_complete(main())