下载器是Requests
解析使用的是正则表达式
效果图:
开始编写代码,new一个py文件
1.requests下载页面 response =requests.get(url) url:当前需要爬取的链接 requests.get()获取页面这里需要注意编码的问题;
就像下面这样： response = requests.get(url) if response.status_code == 200: return response.content.decode("utf-8") return None
这样返回的就是一个string类型的数据
2.except RequestException:捕捉异常为了代码更加健壮，我们在可能发生异常的地方做异常捕获
try: response = requests.get(url) if response.status_code == 200: return response.content.decode("utf-8") return None except RequestException: return None更多异常介绍官网
到这里，我们就可以编写main方法进行调用程序了
代码如下:
# -*- coding: utf-8 -*- import requests from requests.exceptions import RequestException def get_one_page(url): try: response = requests.get(url) if response.status_code == 200: return response.content.decode("utf-8") return None except RequestException: return None def main(): url = \'https://coding.imooc.com/?page=1\' html = get_one_page(url) print(html) if __name__ == \'__main__\': main()这样就可以把页面下载下来了
接着,就是解析页面 3.正则表达式介绍 re.compile()方法:编译正则表达式通过一个正则表达式字符串 编译生成 一个字符串对象
re.findall(pattern,html)方法:找到所有匹配的内容参数:
pattern：编译过的正则表达式
html：用response.content.decode("utf-8")得到的页面内容
完整代码:
# -*- coding: utf-8 -*- import requests import re from requests.exceptions import RequestException def get_one_page(url): try: response = requests.get(url) if response.status_code == 200: return response.content.decode("utf-8") return None except RequestException: return None def parse_one_page(html): pattern = re.compile(\'<div>.*?lecturer-info.*?<span>(.*?)</span>.*?shizhan-intro-box.*?title=".*?">\' \'(.*?)</p>.*?class="grade">(.*?)</span>.*?imv2-set-sns.*?</i>\' \'(.*?)</span>.*?class="big-text">(.*?)</p>.*?shizan-desc.*?>\' \'(.*?)</p>.*?</div>\',re.S) items = re.findall(pattern,html) for item in items: yield { \'teacher\': item[0], \'title\': item[1], \'grade\': item[2], \'people\':item[3], \'score\': item[4], \'describe\': item[5] } def main(): url = \'https://coding.imooc.com/?page=1\' html = get_one_page(url) for item in parse_one_page(html): print(item) if __name__ == \'__main__\': main() 保存解析后的数据到本地文件 4.保存文件操作 with open(\'imooctest.txt\',\'a\',encoding=\'utf-8\') as f with as :打开自动闭合的文件并设立对象f进行操作 参数: imooctest.txt:文件名字 a:追加方式 encoding:编码格式 不这样设置可能保存的数据会乱码 f.write(json.dumps(content,ensure_ascii =False)+\'\n\') json.dumps:将刚才被格式化后的字典转为字符串 ensure_ascii =False 不这样设置可能保存的数据会乱码 +\'\n\' 每条数据为一行代码如下:
# -*- coding: utf-8 -*- import requests import re import json from requests.exceptions import RequestException def get_one_page(url): try: response = requests.get(url) if response.status_code == 200: return response.content.decode("utf-8") return None except RequestException: return None def parse_one_page(html): pattern = re.compile(\'<div>.*?lecturer-info.*?<span>(.*?)</span>.*?shizhan-intro-box.*?title=".*?">\' \'(.*?)</p>.*?class="grade">(.*?)</span>.*?imv2-set-sns.*?</i>\' \'(.*?)</span>.*?class="big-text">(.*?)</p>.*?shizan-desc.*?>\' \'(.*?)</p>.*?</div>\',re.S) items = re.findall(pattern,html) for item in items: yield { \'teacher\': item[0], \'title\': item[1], \'grade\': item[2], \'people\':item[3], \'score\': item[4], \'describe\': item[5] } def write_to_file(content): with open(\'imooctest.txt\',\'a\',encoding=\'utf-8\') as f: f.write(json.dumps(content,ensure_ascii=False)+\'\n\') f.close() def main(): url = \'https://coding.imooc.com/?page=1\' html = get_one_page(url) for item in parse_one_page(html): print(item) write_to_file(item) if __name__ == \'__main__\': main() 5.爬取所有页面并以多进程方式分析页面,会发现,需要爬取的页面如下
https://coding.imooc.com/?page=1 https://coding.imooc.com/?page=2 https://coding.imooc.com/?page=3 https://coding.imooc.com/?page=4我们需要构造这种格式的页面