async 和 await 关键字

import asyncio

# 使用 async def 定义异步函数
async def say_hello():
    print("Hello")
    await asyncio.sleep(1)  # 模拟异步操作
    print("World")

# 运行异步函数
asyncio.run(say_hello())

import asyncio

async def fetch_data():
    print("开始获取数据")
    await asyncio.sleep(2)  # 模拟网络请求
    print("数据获取完成")
    return {"data": 123}

async def main():
    result = await fetch_data()  # 等待异步操作完成
    print(f"获取到的数据: {result}")

asyncio.run(main())

import asyncio
import time

async def task(name, delay):
    print(f"任务 {name} 开始")
    await asyncio.sleep(delay)
    print(f"任务 {name} 完成")
    return f"任务 {name} 结果"

async def main():
    start_time = time.time()
    
    # 同时启动多个任务
    task1 = asyncio.create_task(task("A", 2))
    task2 = asyncio.create_task(task("B", 1))
    task3 = asyncio.create_task(task("C", 3))
    
    # 等待所有任务完成
    results = await asyncio.gather(task1, task2, task3)
    
    end_time = time.time()
    print(f"所有任务完成，耗时: {end_time - start_time:.2f}秒")
    print(f"结果: {results}")

asyncio.run(main())

import asyncio

class AsyncResource:
    async def __aenter__(self):
        print("获取资源")
        await asyncio.sleep(1)
        return self
    
    async def __aexit__(self, exc_type, exc_val, exc_tb):
        print("释放资源")
        await asyncio.sleep(0.5)
    
    async def process(self):
        print("处理资源")
        await asyncio.sleep(2)

async def main():
    async with AsyncResource() as resource:
        await resource.process()

asyncio.run(main())

import asyncio

class AsyncCounter:
    def __init__(self, stop):
        self.current = 0
        self.stop = stop
    
    def __aiter__(self):
        return self
    
    async def __anext__(self):
        if self.current >= self.stop:
            raise StopAsyncIteration
        await asyncio.sleep(0.5)  # 模拟异步操作
        self.current += 1
        return self.current

async def main():
    async for number in AsyncCounter(5):
        print(f"计数: {number}")

asyncio.run(main())

import aiohttp
import asyncio

async def fetch_url(session, url):
    async with session.get(url) as response:
        return await response.text()

async def main():
    urls = [
        "https://httpbin.org/delay/1",
        "https://httpbin.org/delay/2",
        "https://httpbin.org/delay/3"
    ]
    
    async with aiohttp.ClientSession() as session:
        tasks = [fetch_url(session, url) for url in urls]
        results = await asyncio.gather(*tasks)
        
        for url, content in zip(urls, results):
            print(f"{url}: {len(content)} 字符")

asyncio.run(main())

import asyncio
import asyncpg

async def main():
    # 连接数据库
    conn = await asyncpg.connect(
        user='user', password='password',
        database='database', host='localhost'
    )
    
    # 执行查询
    result = await conn.fetch('SELECT * FROM users WHERE active = $1', True)
    
    for row in result:
        print(f"用户: {row['username']}, 邮箱: {row['email']}")
    
    # 关闭连接
    await conn.close()

asyncio.run(main())