Python协程方式的实现及意义笔记分享

from greenlet import greenlet
def func1():
    print(1)        # 第1步：输出 1
    gr2.switch()    # 第3步：切换到 func2 函数
    print(2)        # 第6步：输出 2
    gr2.switch()    # 第7步：切换到 func2 函数，从上一次执行的位置继续向后执行
def func2():
    print(3)        # 第4步：输出 3
    gr1.switch()    # 第5步：切换到 func1 函数，从上一次执行的位置继续向后执行
    print(4)        # 第8步：输出 4
gr1 = greenlet(func1)
gr2 = greenlet(func2)
gr1.switch() # 第1步：去执行 func1 函数

def func1():
    yield 1   #第一步执行这里会生成1
    yield from func2() #这里会跳到func2，然后执行里面的代码，执行完func2函数后会继续以跳转之前的状态继续执行以下代码
    yield 2
def func2():
    yield 3
    yield 4    
# 这里是一个生成器对象
f1 = func1()
# 遍历执行生成器
for item in f1:
    print(item)

import asyncio
#这就是一个用协程实现的函数
@asyncio.coroutine
def func1():
    print(1)
    yield from asyncio.sleep(2)  # 遇到IO耗时操作，自动化切换到tasks中的其他任务
    print(2)
loop = asyncio.get_event_loop()
#执行
loop.run_until_complete(func1())

import asyncio
@asyncio.coroutine
def func1():
    print(1)
    yield from asyncio.sleep(2)  # 遇到IO耗时操作，自动化切换到tasks中的其他任务
    print(2)
@asyncio.coroutine
def func2():
    print(3)
    yield from asyncio.sleep(2) # 遇到IO耗时操作，自动化切换到tasks中的其他任务
    print(4)
tasks = [
    asyncio.ensure_future( func1() ),
    asyncio.ensure_future( func2() )
]
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait(tasks))

import asyncio
async def func1():
    print(1)
    await asyncio.sleep(2)
    print(2)
async def func2():
    print(3)
    await asyncio.sleep(2)
    print(4)
tasks = [
    asyncio.ensure_future(func1()),
    asyncio.ensure_future(func2())
]
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait(tasks))

import requests
def download_image(url):
    print("开始下载:",url)
    # 发送网络请求，下载图片
    response = requests.get(url)
    print("下载完成")
    # 图片保存到本地文件
    file_name = url.rsplit('_')[-1]
    with open(file_name, mode='wb') as file_object:
        file_object.write(response.content)
if __name__ == '__main__':
    url_list = [
        'https://www3.autoimg.cn/newsdfs/g26/M02/35/A9/120x90_0_autohomecar__ChsEe12AXQ6AOOH_AAFocMs8nzU621.jpg',
        'https://www2.autoimg.cn/newsdfs/g30/M01/3C/E2/120x90_0_autohomecar__ChcCSV2BBICAUntfAADjJFd6800429.jpg',
        'https://www3.autoimg.cn/newsdfs/g26/M0B/3C/65/120x90_0_autohomecar__ChcCP12BFCmAIO83AAGq7vK0sGY193.jpg'
    ]
    for item in url_list:
        download_image(item)

import aiohttp
import asyncio
async def fetch(session, url):
    print("发送请求：", url)
    async with session.get(url, verify_ssl=False) as response:
        content = await response.content.read()
        file_name = url.rsplit('_')[-1]
        with open(file_name, mode='wb') as file_object:
            file_object.write(content)
async def main():
    async with aiohttp.ClientSession() as session:
        url_list = [
            'https://www3.autoimg.cn/newsdfs/g26/M02/35/A9/120x90_0_autohomecar__ChsEe12AXQ6AOOH_AAFocMs8nzU621.jpg',
            'https://www2.autoimg.cn/newsdfs/g30/M01/3C/E2/120x90_0_autohomecar__ChcCSV2BBICAUntfAADjJFd6800429.jpg',
            'https://www3.autoimg.cn/newsdfs/g26/M0B/3C/65/120x90_0_autohomecar__ChcCP12BFCmAIO83AAGq7vK0sGY193.jpg'
        ]
        tasks = [asyncio.create_task(fetch(session, url)) for url in url_list]
        await asyncio.wait(tasks)
if __name__ == '__main__':
    asyncio.run(main())