爬虫基本原理(代码片段)

import requests
import re
import time
import hashlib

def get_page(url):
    print(‘GET %s‘ %url)
    try:
        response=requests.get(url)
        if response.status_code == 200:
            return response.content
    except Exception:
        pass

def parse_index(res):
    obj=re.compile(‘class="items.*?<a href="(.*?)"‘,re.S)
    detail_urls=obj.findall(res.decode(‘gbk‘))
    for detail_url in detail_urls:
        if not detail_url.startswith(‘http‘):
            detail_url=‘http://www.xiaohuar.com‘+detail_url
        yield detail_url

def parse_detail(res):
    obj=re.compile(‘id="media".*?src="(.*?)"‘,re.S)
    res=obj.findall(res.decode(‘gbk‘))
    if len(res) > 0:
        movie_url=res[0]
        return movie_url


def save(movie_url):
    response=requests.get(movie_url,stream=False)
    if response.status_code == 200:
        m=hashlib.md5()
        m.update((‘%s%s.mp4‘ %(movie_url,time.time())).encode(‘utf-8‘))
        filename=m.hexdigest()
        with open(r‘./movies/%s.mp4‘ %filename,‘wb‘) as f:
            f.write(response.content)
            f.flush()


def main():
    index_url=‘http://www.xiaohuar.com/list-3-0.html‘
    for i in range(5):
        print(‘*‘*50,i)
        #爬取主页面
        index_page=get_page(index_url.format(i,))
        #解析主页面,拿到视频所在的地址列表
        detail_urls=parse_index(index_page)
        #循环爬取视频页
        for detail_url in detail_urls:
            #爬取视频页
            detail_page=get_page(detail_url)
            #拿到视频的url
            movie_url=parse_detail(detail_page)
            if movie_url:
                #保存视频
                save(movie_url)


if __name__ == ‘__main__‘:
    main()


#并发爬取
from concurrent.futures import ThreadPoolExecutor
import queue
import requests
import re
import time
import hashlib
from threading import current_thread

p=ThreadPoolExecutor(50)

def get_page(url):
    print(‘%s GET %s‘ %(current_thread().getName(),url))
    try:
        response=requests.get(url)
        if response.status_code == 200:
            return response.content
    except Exception as e:
        print(e)

def parse_index(res):
    print(‘%s parse index ‘ %current_thread().getName())
    res=res.result()
    obj=re.compile(‘class="items.*?<a href="(.*?)"‘,re.S)
    detail_urls=obj.findall(res.decode(‘gbk‘))
    for detail_url in detail_urls:
        if not detail_url.startswith(‘http‘):
            detail_url=‘http://www.xiaohuar.com‘+detail_url
        p.submit(get_page,detail_url).add_done_callback(parse_detail)

def parse_detail(res):
    print(‘%s parse detail ‘ %current_thread().getName())
    res=res.result()
    obj=re.compile(‘id="media".*?src="(.*?)"‘,re.S)
    res=obj.findall(res.decode(‘gbk‘))
    if len(res) > 0:
        movie_url=res[0]
        print(‘MOVIE_URL: ‘,movie_url)
        with open(‘db.txt‘,‘a‘) as f:
            f.write(‘%s
‘ %movie_url)
        # save(movie_url)
        p.submit(save,movie_url)
        print(‘%s下载任务已经提交‘ %movie_url)
def save(movie_url):
    print(‘%s SAVE: %s‘ %(current_thread().getName(),movie_url))
    try:
        response=requests.get(movie_url,stream=False)
        if response.status_code == 200:
            m=hashlib.md5()
            m.update((‘%s%s.mp4‘ %(movie_url,time.time())).encode(‘utf-8‘))
            filename=m.hexdigest()
            with open(r‘./movies/%s.mp4‘ %filename,‘wb‘) as f:
                f.write(response.content)
                f.flush()
    except Exception as e:
        print(e)

def main():
    index_url=‘http://www.xiaohuar.com/list-3-0.html‘
    for i in range(5):
        p.submit(get_page,index_url.format(i,)).add_done_callback(parse_index)


if __name__ == ‘__main__‘:
    main()