python協(xié)程之a(chǎn)syncio簡單使用

目錄

簡單的使用

相同和同步的對比

順下載的例子

1.簡單的使用

import asyncio

async def req1():
await asyncio.sleep(1)
print('執(zhí)行 req1')
return 1


async def req2():
print('執(zhí)行 req2')
return 2


async def main():
list = [req1(), req2()]
res = await asyncio.gather(*list)
'''
雖然,req2是先執(zhí)行完的,
但是res返回值的順序, 還是跟list順序保持一致
'''
print(res)


asyncio.get_event_loop().run_until_complete(main())
'''
結(jié)果:
執(zhí)行 req2
執(zhí)行 req1
[1, 2]
'''

2.相似和同時的對比

測試2個請求，同時觸發(fā)請求執(zhí)行的時間短，我是延遲讓請求延遲返回

import asyncio
import time

import requests
from aiohttp import ClientSession


async def fetch(session, param):
async with session.get as resp:
data = await resp.json()
return data


async def req_async():
async with ClientSession() as session:
return await asyncio.gather(fetch(session, 2), \
fetch(session, 1))


def req():
session = requests.Session()
p1, p2 = 2, 1
return [
session.get.json(),
session.get.json()
]


async def main():
s1 = time.time()
v1 = await req_async()
s2 = time.time()
v2 = req()
print(f'異步請求時間：{round(s2-s1,1)}s \
響應(yīng)結(jié)果:{[v["args"]["a"] for v in v1]}')
print(f'同步請求時間：{round(time.time()-s2,1)}s \
響應(yīng)結(jié)果:{[v["args"]["a"] for v in v2]}')


if __name__ == '__main__':
asyncio.get_event_loop().run_until_complete(main())
'''
結(jié)果:
異步請求時間：3.2s 響應(yīng)結(jié)果:['2', '1']
同步請求時間：7.9s 響應(yīng)結(jié)果:['2', '1']
'''


3.相關(guān)下載的例子

看似請求、極大的文件限制、意外保存

async def download(sem, page: int, folder: str, session: ClientSession):
async with sem:
async with session.get(url, params={'page': page}) as resp:
async with aiofiles.open(f'{folder}/{page}.json', mode='w') as f:
await f.write(await resp.text())
return page


async def main():
# 請求url參數(shù)列表
url_pages = range(1, 5)
# 創(chuàng)建文件夾data
folder_name = 'data'
if not os.path.exists(folder_name):
os.makedirs(folder_name)
# 限制并發(fā)數(shù)量
sem = asyncio.Semaphore(50)
# 異步請求，并保存到文件
async with ClientSession(connector=TCPConnector(limit=5),
timeout=ClientTimeout(300)) as session:
tasks = []
for page in url_pages:
tasks.append(download(sem, page, folder_name, session))
result = await asyncio.gather(*tasks)
exp = set(url_pages)
act = set(result)
if exp == act:
print(f'全部下載完成')
else:
print(f'未成功：{exp - act}，成功：{exp & act}')


if __name__ == '__main__':
asyncio.get_event_loop().run_until_complete(main())




審核編輯：劉清