python爬蟲即編寫python指令碼處理web網頁，使用特定的演算法，抓取所需要的內容：

以下以爬取糗事百科的段子為例進行說明，程式碼如下：

import urllib.request
import re



def jokeCrawler(url):
    headers = {
        "User-Agent": "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36"
    }

    req = urllib.request.Request(url, headers=headers)
    response = urllib.request.urlopen(req)
    html = response.read().decode("utf-8")
    # HTML = str(response.read())

    pat = r'<div class="author clearfix">(.*?)<span class="stats-vote"><i class="number">'
    re_joke = re.compile(pat, re.S)
    divList = re_joke.findall(html)
    # print(divList)
    # print(len(divList))

    dic = {}
    for div in divList:
        re_u = re.compile(r'<h2>(.*?)</h2>', re.S)
        username = re_u.findall(div)
        # print(type(username))
        username = username[0]
        # print(username)

        re_d = re.compile(r'<div class="content">\n<span>(.*?)</span>', re.S)
        duanzi = re_d.findall(div)
        # print(type(username))
        duanzi = duanzi[0]
        # print(duanzi)

        dic[username] = duanzi
    return dic


    # with open(r"D:\pythonPro\star\pacong\file\file3.html", "w", encoding='utf-8') as f:
    #     f.write(HTML)

url = "https://www.qiushibaike.com/text/page/2/"
info = jokeCrawler(url)
for k, v in info.items():
    print(k + "說\n" + v)
 

其中：表示式 .* 就是單個字元匹配任意次，即貪婪匹配。 表示式 .*? 是滿足條件的情況只匹配一次，即最小匹配。