-安裝爬蟲需要的庫?

C:python37>pip install requests?
Collecting requests?
? Downloading https://files.pythonhosted.org/packages/7d/e3/20f...84b/requests-2.21.0-py2.py3-none-any.whl (57kB)?
??? 100% |████████████████████████████████| 61kB 225kB/s?
Collecting urllib3<1.25,>=1.21.1 (from requests)?
? Downloading https://files.pythonhosted.org/packages/62/00/ee1...79e/urllib3-1.24.1-py2.py3-none-any.whl (118kB)?
??? 100% |████████████████████████████████| 122kB 585kB/s?
Collecting idna<2.9,>=2.5 (from requests)?
? Downloading https://files.pythonhosted.org/packages/14/2c/cd55...4c9/idna-2.8-py2.py3-none-any.whl (58kB)?
??? 100% |████████████████████████████████| 61kB 1.3MB/s?
Collecting chardet<3.1.0,>=3.0.2 (from requests)?
? Downloading https://files.pythonhosted.org/packages/bc/a9/01ffe...b8/chardet-3.0.4-py2.py3-none-any.whl (133kB)?
??? 100% |████████████████████████████████| 143kB 267kB/s?
Collecting certifi>=2017.4.17 (from requests)?
? Downloading https://files.pythonhosted.org/packages/9f/e0/ac...e8a/certifi-2018.11.29-py2.py3-none-any.whl (154kB)?
??? 100% |████████████████████████████████| 163kB 273kB/s?
Installing collected packages: urllib3, idna, chardet, certifi, requests?
Successfully installed certifi-2018.11.29 chardet-3.0.4 idna-2.8 requests-2.21.0 urllib3-1.24.1?


什么是Urllib?

Python內置的Http請求庫?
urllib.request 請求模塊? 　　模擬瀏覽器?
urllib.error 異常處理模塊?
urllib.parse url解析模塊? 　　工具模塊，如：拆分、合并?
urllib.robotparser robots.txt??? 解析模塊　?
　?
urllib是Python自帶的標準庫，無需安裝，直接可以用。?
提供了如下功能：?
??? 網頁請求?
??? 響應獲取?
??? 代理和cookie設置?
??? 異常處理?
??? URL解析?
爬蟲所需要的功能，基本上在urllib中都能找到，學習這個標準庫，可以更加深入的理解后面更加便利的requests庫。?

2和3的區別?
Python2?
import urllib2?
response = urllib2.urlopen('http://www.baidu.com');?

Python3?
import urllib.request?
response =urllib.request.urlopen('http://www.baidu.com');?