Python使用asyncio+aiohttp异步爬取猫眼电影专业版

时间：2020-12-06 19:57:44

asyncio是从pytohn3.4开始添加到标准库中的一个强大的异步并发库，可以很好地解决python中高并发的问题，入门学习可以参考官方文档

并发访问能极大的提高爬虫的性能，但是requests访问网页是阻塞的，无法并发，所以我们需要一个更牛逼的库 aiohttp ，它的用法与requests相似，可以看成是异步版的requests，下面通过实战爬取猫眼电影专业版来熟悉它们的使用：

1. 分析

分析网页源代码发现猫眼专业版是一个动态网页，其中的数据都是后台传送的，打开F12调试工具，再刷新网页选择XHR后发现第一条就是后台发来的电影数据，由此得到接口 https://box.maoyan.com/promovie/api/box/second.json?beginDate=日期

 
Python使用asyncio+aiohttp异步爬取猫眼电影专业版
在这里插入图片描述

2. 异步爬取

创建20个任务来并发爬取20天的电影信息并写入csv文件，同时计算一下耗费的时间

import asyncio

from aiohttp import ClientSession

import aiohttp

import time

import csv

import ssl

ssl._create_default_https_context = ssl._create_unverified_context

headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) '

                             'AppleWebKit/537.36 (KHTML, like Gecko) '

                             'Chrome/67.0.3396.99 Safari/537.36'}

# 协程函数，完成一个无阻塞的任务

async def get_one_page(url):

	try:

		conn = aiohttp.TCPConnector(verify_ssl=False)  # 防止ssl报错

		async with aiohttp.ClientSession(connector=conn) as session:  # 创建session

			async with session.get(url, headers=headers) as r:

				# 返回解析为字典的电影数据

				return  await r.json()

	except Exception as e:

		print('请求异常： ' + str(e))

		return {}

# 解析函数，提取每一条内容并写入csv文件

def parse_one_page(movie_dict, writer):

	try:

		movie_list = movie_dict['data']['list']

		for movie in movie_list:

			movie_name = movie['movieName']

			release = movie['releaseInfo']

			sum_box = movie['sumBoxInfo']

			box_info = movie['boxInfo']

			box_rate = movie['boxRate']

			show_info = movie['showInfo']

			show_rate = movie['showRate']

			avg_show_view = movie['avgShowView']

			avg_seat_view = movie['avgSeatView']

			writer.writerow([movie_name, release, sum_box, box_info, box_rate,

			                show_info, show_rate, avg_show_view, avg_seat_view])

		return('写入成功')

	except Exception as e:

		return('解析异常： ' + str(e))

# 并发爬取

async def main():

    # 待访问的20个URL链接

    urls = ['https://box.maoyan.com/promovie/api/box/second.json?beginDate=201904{}{}'.format(i, j) for i in range(1, 3) for j in range(10)]

    # 任务列表

    tasks = [get_one_page(url) for url in urls]

    # 并发执行并保存每一个任务的返回结果

    results = await asyncio.gather(*tasks)

    # 处理每一个结果

    with open('pro_info.csv', 'w') as f:

        writer = csv.writer(f)

        for result in results:

            print(parse_one_page(result, writer))

if __name__ == "__main__":

	start = time.time()

	# asyncio.run(main())

	# python3.7之前的写法

	loop = asyncio.get_event_loop()

	loop.run_until_complete(main())

	loop.close()

	print(time.time()-start)

　　

 

3. 对比同步爬取

import requests

import csv

import time

headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) '

                             'AppleWebKit/537.36 (KHTML, like Gecko) '

                             'Chrome/67.0.3396.99 Safari/537.36'}

def get_one_page(url):

    try:

        r = requests.get(url, headers=headers)

        r.raise_for_status()

        r.encoding = r.apparent_encoding

        return r.json()

    except Exception as e:

        print('请求异常： ' + e)

        return {}

def parse_one_page(movie_dict, writer):

    try:

        movie_list = movie_dict['data']['list']

        for movie in movie_list:

            movie_name = movie['movieName']

            release = movie['releaseInfo']

            sum_box = movie['sumBoxInfo']

            box_info = movie['boxInfo']

            box_rate = movie['boxRate']

            show_info = movie['showInfo']

            show_rate = movie['showRate']

            avg_show_view = movie['avgShowView']

            avg_seat_view = movie['avgSeatView']

            writer.writerow([movie_name, release, sum_box, box_info, box_rate,

                            show_info, show_rate, avg_show_view, avg_seat_view])

        print('写入成功')

    except Exception as e:

        print('解析异常： ' + e)

def main():

    # 待访问的20个URL链接

    urls = ['https://box.maoyan.com/promovie/api/box/second.json?beginDate=201903{}{}'.format(i, j) for i in range(1, 3) for j in  range(10)]

    with open('out/pro_info.csv', 'w') as f:

        writer = csv.writer(f)

        for url in urls:

            # 逐一处理

            movie_dict = get_one_page(url)

            parse_one_page(movie_dict, writer)

if __name__ == '__main__':

    a = time.time()

    main()

    print(time.time() - a)
 
Python使用asyncio+aiohttp异步爬取猫眼电影专业版
在这里插入图片描述

可以看到使用asyncio+aiohttp的异步爬取方式要比简单的requests同步爬取快上不少，尤其是爬取大量网页的时候，这种差距会非常明显。

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