Python爬虫知识点二
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一。request库
import json import requests from io import BytesIO #显示各种函数相当于api # print(dir(requests)) url = \'http://www.baidu.com\' r = requests.get(url) print(r.text) print(r.status_code) print(r.encoding)
结果：
# 传递参数：不如http://aaa.com?pageId=1&type=content params = {\'k1\':\'v1\', \'k2\':\'v2\'} r = requests.get(\'http://httpbin.org/get\', params) print(r.url) 结果：
# 二进制数据 # r = requests.get(\'http://i-2.shouji56.com/2015/2/11/23dab5c5-336d-4686-9713-ec44d21958e3.jpg\') # image = Image.open(BytesIO(r.content)) # image.save(\'meinv.jpg\') # json处理 r = requests.get(\'https://github.com/timeline.json\') print(type(r.json)) print(r.text)
结果：
# 原始数据处理 # 流式数据写入 r = requests.get(\'http://i-2.shouji56.com/2015/2/11/23dab5c5-336d-4686-9713-ec44d21958e3.jpg\', stream = True) with open(\'meinv2.jpg\', \'wb+\') as f: for chunk in r.iter_content(1024): f.write(chunk) # 提交表单 form = {\'username\':\'user\', \'password\':\'pass\'} r = requests.post(\'http://httpbin.org/post\', data = form) print(r.text)
结果：参数以表单形式提交，所以参数放在form参数中
r = requests.post(\'http://httpbin.org/post\', data = json.dumps(form)) print(r.text)
结果：参数不是以form表单提交的，所以放在json字段中
# cookie url = \'http://www.baidu.com\' r = requests.get(url) cookies = r.cookies #cookie实际上是一个字典 for k, v in cookies.get_dict().items(): print(k, v) 结果：cookie实际上是一个键值对
cookies = {\'c1\':\'v1\', \'c2\': \'v2\'} r = requests.get(\'http://httpbin.org/cookies\', cookies = cookies) print(r.text) 结果：
# 重定向和重定向历史 r = requests.head(\'http://github.com\', allow_redirects = True) print(r.url) print(r.status_code) print(r.history) 结果：通过301定向
# # 代理 # # proxies = {\'http\': \',,,\', \'https\': \'...\'} # r = requests.get(\'...\', proxies = proxies)
二。BeautifulSoup库
html:举例如下
<html><head><title>The Dormouse\'s story</title></head> <body> <p class="title" name="dromouse"><b>The Dormouse\'s story</b></p> <p class="story">Once upon a time there were three little sisters; and their names were <a href="http://example.com/elsie" class="sister" id="link1"><!-- Elsie --></a>, <a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and <a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>; and they lived at the bottom of a well.</p> <p class="story">...</p>
解析代码如下：
from bs4 import BeautifulSoup soup = BeautifulSoup(open(\'test.html\'))
#使html文本更加结构化 # print(soup.prettify()) # Tag print(type(soup.title))
结果：bs4的一个类
print(soup.title.name)
print(soup.title)
结果如下：
# String print(type(soup.title.string)) print(soup.title.string) 结果如下：只显示标签里面内容
# Comment print(type(soup.a.string)) print(soup.a.string)
结果：显示注释中的内容，所以有时需要判断获取到的内容是不是注释
# # \'\'\' for item in soup.body.contents: print(item.name) 结果：body下面有三个item
# CSS查询 print(soup.select(\'.sister\'))
结果：样式选择器返回带有某个样式的所有内容 结果为一个list
print(soup.select(\'#link1\'))
结果：ID选择器，选择ID等于link1的内容
print(soup.select(\'head > title\')) 结果：
a_s = soup.select(\'a\') for a in a_s: print(a)
结果：标签选择器，选择所有a标签的
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