Python开发之爬虫实战

Requests+正则表达式爬取电影

 1、目标站点分析

• 抓取单页内容：利用requests请求目标站点，得到单个网页HTML代码，返回结果
• 正则表达式分析：根据HTML代码分析得到电影的名称、主演、上映时间、评分、图片链接等信息
• 保存至文件：通过文件的形式将结果保存，每一部电影一个结果一行json字符串
• 开启循环及多线程：对多页内容遍历，开启多线程提高抓取速度。

2、实战

import requests
from requests.exceptions import RequestException
from multiprocessing import Pool
import re,json
def get_one_page(url):
    try:
        headers = {
            'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36'
        } # 加headers非常必要，不加很可能会被禁掉
        response = requests.get(url,headers=headers)
        if response.status_code == 200:
            return response.text
        return None
    except RequestException:
        return None

def parse_one_page(html):
    pattern = re.compile('<dd>.*?board-index.*?>(\d+)</i>.*?data-src="(.*?)".*?name"><a'
                         +'.*?>(.*?)</a>.*?star">(.*?)</p>.*?releasetime">(.*?)</p>'
                          +'.*?integer">(.*?)</i>.*?fraction">(.*?)</i>.*?</dd>',re.S)
    items = re.findall(pattern,html)
    for item in items:
        yield {
            'index':item[0],
            'image':item[1],
            'title':item[2],
            'actor':item[3].strip()[3:],
            'time':item[4].strip()[5:],
            'score':item[5]+item[6]
        }

def write_to_file(content):
    with open('result.txt','a',encoding='utf8') as f:
        f.write(json.dumps(content,ensure_ascii=False) + '\n') # content是字典的形式，需要用json进行转换

def main(offset):
    url = 'http://maoyan.com/board/4?offset=' + str(offset)
    html = get_one_page(url)
    for item in parse_one_page(html):
        # print(item)
        write_to_file(item) # 写到文件
if __name__ == '__main__':
    # for i in range(10):
    #     main(i*10)
    pool = Pool()
    pool.map(main, [i*10 for i in range(10)]) # 利用多进程抓取，提高效率

抓取街拍美图实例

这个实例需要的库以及数据库有：请求库requests，解析库BeautifulSoup和正则，存储的数据库是MongoDB，需要pymongo库

1、流程框架：

• 抓取索引页内容：利用requests请求目标站点内容，得到索引网页HTML代码，返回结果
• 抓取详情页内容：解析返回结果，得到详情页的链接，并进一步抓取详情页的信息
• 下载图片与保存数据：将图片下载到本地，并把页面信息及图片URl保存到MongoDB
• 开启循环及多线程：对多页内容进行遍历，开启多线程提高抓取速度

2、实战

 spider.py

import requests
from requests.exceptions import RequestException
from urllib.parse import urlencode
import json,re
from bs4 import BeautifulSoup
import pymongo
from config import *
import os,hashlib
from multiprocessing import Pool

client = pymongo.MongoClient(MONGO_URL,connect=False)
db = client[MONGO_DB]

def get_page_index(offset,keyword):
    data = {
        'offset': offset,
        'format': 'json',
        'keyword': keyword,
        'autoload': 'true',
        'count': 20,
        'cur_tab': 1,
        'from':'search_tab'
    }
    url = 'https://www.toutiao.com/search_content/?' + urlencode(data)
    headers = {
        'user-agent':'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36'
    }
    try:
        response = requests.get(url,headers=headers)
        if response.status_code == 200:
            return response.text
        return None
    except RequestException:
        print('请求索引页失败')
        return None

def parse_page_index(html):
    data = json.loads(html)
    if data and 'data' in data.keys():
        for item in data.get('data'):
            yield item.get('article_url')

def get_page_detail(url):
    headers = {
        'user-agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36'
    }
    try:
        if url:
            response = requests.get(url,headers=headers)
            if response.status_code == 200:
                return response.text
            return None
    except RequestException:
        print('详情页出错',url)
        return None

def parse_page_deatil(html,url):
    soup = BeautifulSoup(html,'lxml')
    title = soup.select('title')[0].get_text()
    # print(title)
    images_pattern = re.compile('JSON.parse\("(.*?)"\)',re.S)
    result = re.search(images_pattern, html)
    if result:
        data = result.group(1)
        data = data.replace('\\"', '"')
        data = json.loads(data)
        if data and 'sub_images' in data.keys():
            sub_images = data.get('sub_images')
            images = [item.get('url') for item in sub_images]
            for image in images:download_image(image)
            return {
                'title':title,
                'url':url,
                'images':images
            }

def save_to_mongo(result):
    if db[MONGO_TABLE].insert(result):
        print('成功存储到MongoDB')
        return True
    return False

def download_image(url):
    try:
        response = requests.get(url)
        if response.status_code == 200:
            save_image(response.content)
        return None
    except RequestException:
        print('请求图片失败')
        return None

def save_image(content):
    file_path = '{0}/{1}.{2}'.format(os.getcwd(),hashlib.md5(content).hexdigest(),'.jpg') # 路径拼接
    if not os.path.exists(file_path):
        with open(file_path,'wb') as f:
            f.write(content)

def main(offset):
    html = get_page_index(offset,KEYWORD)
    for url in parse_page_index(html):
        html = get_page_detail(url)
        if html:
            result = parse_page_deatil(html,url)
            if result:save_to_mongo(result)

if __name__ == '__main__':
    groups = [x*20 for x in range(GROUP_START,GROUP_END + 1)]
    pool = Pool()
    pool.map(main,groups)

config.py:配置文件

MONGO_URL='localhost'
MONGO_DB='toutiao'
MONGO_TABLE='toutiao'

GROUP_START=1
GROUP_END=20
KEYWORD='街拍'