链接:https://pan.quark.cn/s/c6df12a6efcc
本文将介绍如何利用AIOHTTP模块提高网络请求效率,以及如何编写一个异步下载图片的程序,并展示如何通过AIOHTTP和AIO files的异步功能优化Python爬虫程序的读写操作。
00:00 - AIOHTTP模块:提高网络请求效率
AIOHTTP模块作为一种异步网络请求库,与传统的同步请求模块相比,能够显著提高网络请求的效率。下面是一个简单的示例,展示了如何使用AIOHTTP进行图片下载。
安装AIOHTTP
首先,确保已安装AIOHTTP模块,可以使用以下命令进行安装:
pip install aiohttp
编写异步下载图片的程序
我们将定义一个名为download
的协程函数用于下载图片,并在主程序中使用异步方法来调用该函数。
import aiohttp
import asyncio
import aiofiles
async def download(url, session, dest):
async with session.get(url) as response:
if response.status == 200:
f = await aiofiles.open(dest, mode='wb')
await f.write(await response.read())
await f.close()
print(f"Downloaded {url} to {dest}")
else:
print(f"Failed to download {url}")
async def main(urls):
async with aiohttp.ClientSession() as session:
tasks = []
for idx, url in enumerate(urls):
dest = f"image_{idx}.jpg"
task = asyncio.create_task(download(url, session, dest))
tasks.append(task)
await asyncio.gather(*tasks)
if __name__ == "__main__":
image_urls = [
"http://example.com/image1.jpg",
"http://example.com/image2.jpg",
"http://example.com/image3.jpg"
]
asyncio.run(main(image_urls))
04:51 - 调用AIOHTTP模块实现图片下载
使用AIOHTTP模块通过client session方法发起请求,并利用异步IO实现图片的下载与保存。以下是示例代码:
import aiohttp
import asyncio
import aiofiles
async def fetch_and_save(url, session, path):
async with session.get(url) as response:
if response.status == 200:
async with aiofiles.open(path, 'wb') as f:
await f.write(await response.read())
print(f"Saved image from {url} to {path}")
else:
print(f"Failed to fetch image from {url}")
async def download_images(urls):
async with aiohttp.ClientSession() as session:
tasks = []
for idx, url in enumerate(urls):
path = f'image_{idx}.jpg'
task = asyncio.create_task(fetch_and_save(url, session, path))
tasks.append(task)
await asyncio.gather(*tasks)
if __name__ == '__main__':
image_urls = [
"http://example.com/image1.jpg",
"http://example.com/image2.jpg",
"http://example.com/image3.jpg"
]
asyncio.run(download_images(image_urls))
09:30 - 使用AIO异步功能提高Python爬虫效率
下面展示如何利用AIOHTTP和AIO files的异步功能优化Python爬虫程序的读写操作。
安装依赖
确保已安装aiohttp和aiofiles模块。
pip install aiohttp aiofiles
编写异步爬虫程序
import aiohttp
import asyncio
import aiofiles
async def fetch_page(url, session):
async with session.get(url) as response:
if response.status == 200:
return await response.text()
else:
print(f"Failed to fetch {url}")
return None
async def save_page(content, path):
async with aiofiles.open(path, 'w') as f:
await f.write(content)
print(f"Saved page to {path}")
async def crawl(urls):
async with aiohttp.ClientSession() as session:
tasks = []
for idx, url in enumerate(urls):
path = f'page_{idx}.html'
task = asyncio.create_task(fetch_and_save(url, session, path))
tasks.append(task)
await asyncio.gather(*tasks)
async def fetch_and_save(url, session, path):
content = await fetch_page(url, session)
if content:
await save_page(content, path)
if __name__ == "__main__":
urls = [
"http://example.com/page1",
"http://example.com/page2",
"http://example.com/page3"
]
asyncio.run(crawl(urls))
上述代码展示了如何使用AIOHTTP和AIO files的异步功能来获取网页内容并将其保存至本地文件中。通过引入异步I/O处理,大幅提升了数据处理速度与程序响应性。
通过这些示例,您可以深入理解并应用Python的异步编程机制,以提升程序执行效率。