python爬虫的urllib库详解

1.什么是Urllib

python内置的HTTP请求库

• urllib.request 请求模块
• urllib.error 异常处理模块
• urllib.parse url解析模块
• urllib.robotparser robots.txt 解析模块

2.相对于Python2的变化

Python2
import urllib2
response = urllib2.urlopen(“http://www.baidu.com”)

Python3
import urllib.request
response = urllib.request.urlopen(“http://www.baidu.com”)

3.urllib用法讲解

3.1urlopen

urllib.request.urlopen(url, data=None, [timeout, ]*, cafile=None, capath=None, cadefault=False, context=None)

3.1.1实现网页get请求

import urllib.request
response = urllib.request.urlopen('http://www.baidu.com')
print(response.read().decode('utf-8'))

3.1.2 请求时加载数据

import urllib.parse
import urllib.request
data = bytes(urllib.parse.urlencode({'word': 'hello'}), encoding='utf8')
response = urllib.request.urlopen('http://httpbin.org/post', data=data)
print(response.read())

3.1.3超时请求设置

#超时请求设置
import urllib.request
response = urllib.request.urlopen('http://httpbin.org/get', timeout=1)
print(response.read())

3.1.4判断超时请求

#判断超时请求
import socket
import urllib.request
import urllib.error
try:
    response = urllib.request.urlopen('http://httpbin.org/get', timeout=0.1)
except urllib.error.URLError as e:
    if isinstance(e.reason, socket.timeout):
        print('TIME OUT')

3.2响应

3.2.1响应类型

import urllib.request
response = urllib.request.urlopen('https://www.baidu.com')
print(type(response))

3.2.2状态码、响应头

import urllib.request
response = urllib.request.urlopen('https://www.baidu.com')
print(response.status)#状态码
print(response.getheaders())#所有显示头
print(response.getheader('Server'))

import urllib.request
response = urllib.request.urlopen('https://www.baidu.com')
print(response.read().decode('utf-8'))  #网页的源代码

3.3Request

3.3.1使用Request来请求网页

import urllib.request
request = urllib.request.Request('https://www.baidu.com')
response = urllib.request.urlopen(request)
print(response.read().decode('utf-8'))

3.3.2通过Request请求参数来请求网页

from urllib import request, parse
# 通过这是请求参数来请求网页
url = 'http://httpbin.org/post'
headers = {
    'User-Agent': 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)',
    'Host': 'httpbin.org'
}
dict = {
    'name': 'Germey'
}
data = bytes(parse.urlencode(dict), encoding='utf8') #formdata
req = request.Request(url=url, data=data, headers=headers, method='POST')
response = request.urlopen(req)
print(response.read().decode('utf-8'))

3.3.2通过Request.add_header方法来请求网页

from urllib import request, parse

url = 'http://httpbin.org/post'
dict = {
    'name': 'Germey'
}
data = bytes(parse.urlencode(dict), encoding='utf8')
req = request.Request(url=url, data=data, method='POST')
#通过Request.add_header方法来请求网页
req.add_header('User-Agent', 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)')
response = request.urlopen(req)
print(response.read().decode('utf-8'))

3.4Handler

3.4.1代理:使用代理，来伪装IP地址

#handler相当于一个额外的工具，来处理一些设置
import urllib.request
#使用代理，来伪装IP地址
proxy_handler = urllib.request.ProxyHandler({
    'http': 'http://127.0.0.1:9743',
    'https': 'https://127.0.0.1:9743'
})
opener = urllib.request.build_opener(proxy_handler)
response = opener.open('http://httpbin.org/get')
print(response.read())

3.4.2Cookie:cookies用来维持登录状态

import http.cookiejar, urllib.request
#cookies用来维持登录状态
cookie = http.cookiejar.CookieJar()
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(handler)
response = opener.open('http://www.baidu.com')
for item in cookie:
    print(item.name+"="+item.value)

import http.cookiejar, urllib.request
#cookies保存成文本文件，保存格式mozilla
filename = "cookie.txt"
cookie = http.cookiejar.MozillaCookieJar(filename)
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(handler)
response = opener.open('http://www.baidu.com')
cookie.save(ignore_discard=True, ignore_expires=True)

import http.cookiejar, urllib.request
#cookies保存成文本文件，保存格式lwp
filename = 'cookie.txt'
cookie = http.cookiejar.LWPCookieJar(filename)
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(handler)
response = opener.open('http://www.baidu.com')
cookie.save(ignore_discard=True, ignore_expires=True)

import http.cookiejar, urllib.request
#读取cookies
cookie = http.cookiejar.LWPCookieJar()
cookie.load('cookie.txt', ignore_discard=True, ignore_expires=True)
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(handler)
response = opener.open('http://www.baidu.com')
print(response.read().decode('utf-8'))

3.5异常处理

3.5.1读出异常

from urllib import request, error
try:
    response = request.urlopen('http://cuiqingcai.com/index.htm')
except error.URLError as e:
    print(e.reason)

from urllib import request, error

try:
    response = request.urlopen('http://cuiqingcai.com/index.htm')
except error.HTTPError as e:
    print(e.reason, e.code, e.headers, sep='\n')
except error.URLError as e:
    print(e.reason)
else:
    print('Request Successfully')

import socket
import urllib.request
import urllib.error

try:
    response = urllib.request.urlopen('https://www.baidu.com', timeout=0.01)
except urllib.error.URLError as e:
    print(type(e.reason))
    if isinstance(e.reason, socket.timeout):
        print('TIME OUT')

3.6URL解析

3.6.1urlparse：将网址拆分成不同意义的字典

urllib.parse.urlparse(urlstring, scheme=’’, allow_fragments=True)
#网址，协议类型，锚点链接

from urllib.parse import urlparse
#解析网址
result = urlparse('http://www.baidu.com/index.html;user?id=5#comment')
print(type(result), result)

from urllib.parse import urlparse

result = urlparse('www.baidu.com/index.html;user?id=5#comment', scheme='https')
print(result)

from urllib.parse import urlparse

result = urlparse('http://www.baidu.com/index.html;user?id=5#comment', scheme='https')
print(result)

from urllib.parse import urlparse

result = urlparse('http://www.baidu.com/index.html;user?id=5#comment', allow_fragments=False)
print(result)

from urllib.parse import urlparse

result = urlparse('http://www.baidu.com/index.html#comment', allow_fragments=False)
print(result)

3.6.2urlunparse：urlparse的反编译

from urllib.parse import urlunparse
#urlparse的反函数
data = ['http', 'www.baidu.com', 'index.html', 'user', 'a=6', 'comment']
print(urlunparse(data))

3.6.3urljoin：拼接网址

from urllib.parse import urljoin
#用来拼接url
print(urljoin('http://www.baidu.com', 'FAQ.html'))
print(urljoin('http://www.baidu.com', 'https://cuiqingcai.com/FAQ.html'))
print(urljoin('http://www.baidu.com/about.html', 'https://cuiqingcai.com/FAQ.html'))
print(urljoin('http://www.baidu.com/about.html', 'https://cuiqingcai.com/FAQ.html?question=2'))
print(urljoin('http://www.baidu.com?wd=abc', 'https://baidu.com/index.php'))
print(urljoin('http://www.baidu.com', '?category=2#comment'))
print(urljoin('www.baidu.com', '?category=2#comment'))
print(urljoin('www.baidu.com#comment', '?category=2'))

3.6.4urlencode：把一个字典对象转换成get请求参数

from urllib.parse import urlencode
#把一个字典对象转换成get请求参数
params = {
    'name': 'germey',
    'age': 22
}
base_url = 'http://www.baidu.com?'
url = base_url + urlencode(params)
print(url)