python爬虫笔记（二）request库的使用（实例：贴吧爬虫）

1. requests库安装

推荐使用anaconda，自带

2. requests使用

import requests

r = requests.get("http://www.baidu.com")
print(r.status_code)

r.encoding = 'utf-8'
print(r.text)

2.1 Requests库的get()方法

2.2 Response对象

（1）判断请求是否成功

assert response.status_code == 200

2.3 requests模块发送带headers的请求

（1）如果没有模拟浏览器，对方服务器只会返回一小部分内容

（2）为了模拟浏览器，所以需要发送带header请求

2.4 requests发送带参数的请求

（1）url编码格式

https%3A%2F%2Fwww.baidu.com%2Fs%3Fwd%3Dpython&logid=8596791949931086675&signature=aa5a72defcf92845bdcdac2e55e0aab3&timestamp=1579276087

解码：

https://www.baidu.com/s?wd=python&logid=8596791949931086675&signature=aa5a72defcf92845bdcdac2e55e0aab3&timestamp=1579276087

（2）字符串格式化另一种方式

import requests

headers = {"User-Agent" : "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.88 Safari/537.36"}

ps = {"wd":"python"}
url_tmp = "https://www.baidu.com/s?wd={}".format("python")

r = requests.get(url=url_tmp, headers=headers)
print(r.status_code)
print(r.request.url)

3. 通用代码框架

4. 几个例子

5. 实例：贴吧爬虫

# -*- coding: utf-8 -*-

import requests

class TiebaSpider(object):
    def __init__(self, tieba_name):
        self.tieba_name = tieba_name
        self.url_temp = "http://tieba.baidu.com/f?kw="+tieba_name+"&ie=utf-8&pn={}"
        self.headers = {"User-Agent": "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.88 Safari/537.36"}
    
    def get_url_list(self):     # 构造url列表
        url_list = []
        for i in range(100):
            url_list.append(self.url_temp.format(i*50)) 
        return url_list
        
    def parse_url(self, url):   # 2.遍历，发送请求，获取响应
        print(url)
        response = requests.get(url, headers=self.headers)
        return response.content.decode()
        
    def save_html(self, html_str, page_num):   # 3.保存html字符串
        file_path = "{}_第{}页.html".format(self.tieba_name, page_num)
        with open(file_path, "w", encoding="utf-8") as f:      # "成果_第1页.html"
            f.write(html_str)
        
    def run(self):  # 实现主要逻辑
        # 1.构造url列表
        url_list = self.get_url_list()
        # 2.遍历，发送请求，获取响应
        for url in url_list:
            html_str = self.parse_url(url)
            # 3.保存
            page_num = url_list.index(url) + 1   # 页码数
            self.save_html(html_str, page_num)
        
        
if __name__ == '__main__':
    tieba_spider = TiebaSpider("成果")
    tieba_spider.run()