爬虫常用库

作者: HHHHUA | 来源:发表于2019-01-31 11:51 被阅读40次

[[toc]]

一、常用库

requests 做请求的时候用到: requests.get("url")
selenium 自动化会用到
lxml
beautifulsoup
pyquery 网页解析库，语法和jquery非常像
pymysql 存储库,操作mysql数据的
pymongo 操作MongoDB 数据库
redis 非关系型数据库
jupyter 在线记事本

二、什么是Urllib

Python内置的Http请求库
urllib.request 请求模块模拟浏览器发送请求
urllib.error 异常处理模块
urllib.parse url解析模块工具模块，如：拆分、合并
urllib.robotparser robots.txt 解析模块

python2 和 python3 的区别

Python2:

    import urllib2
    response = urllib2.urlopen('http://www.baidu.com');

Python3

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

用法：

# urlOpen 发送请求给服务器。
urllib.request.urlopen(url,data=None[参数],[timeout,]*,cafile=None,capath=None,cadefault=false,context=None)

例子：

# 例1：
import urllib.requests

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

# 例2：
import urllib.request
import urllib.parse

data=bytes(urllib.parse.urlencode({'word':'hello'}),encoding='utf8')
response=urllib.reqeust.urlopen('http://httpbin.org/post',data=data)
print(response.read())
# 注：加data就是post发送，不加就是以get发送。

# 例3：

# 超时测试
import urllib.request
response =urllib.request.urlopen('http://httpbin.org/get',timeout=1)
print(response.read())

# -----正常
import socket
import urllib.reqeust
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')

# 这是就是输出 TIME OUT

响应类型

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

输出:print(type(response))

状态码、响应头

import urllib.request
response = urllib.request.urlopen('http://www.python.org')
print(response.status)  // 正确返回200 
print(response.getheaders())    //返回请求头
print(response.getheader('Server'))

三、Request 可以添加headers

import urllib.request

request=urllib.request.Request('https://python.org')
response=urllib.request.urlopen(request)
print(response.read().decode('utf-8'))

例子：

 from urllib import request,parse

url='http://httpbin.org/post'
headers={
　　User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.75 Safari/537.36
　　Host:httpbin.org
}
dict={
　　'name':'Germey'
}
data=bytes(parse.urlencode(dict),encoding='utf8')
req= request.Request(url=url,data=data,headers=headers,method='POST')
response = request.urlopen(req)
print(response.read().decode('utf-8'))

四、代理

import urllib.request
proxy_handler =urllib.request.ProxyHandler({
　　'http':'http://127.0.0.1:9743',
　　'https':'http://127.0.0.1:9743',
})
opener =urllib.request.build_opener(proxy_handler)
response= opener.open('http://httpbin.org/get')
print(response.read())

五、Cookie

import http.cookiejar,urllib.request

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)

第一种保存cookie方式

　　import http.cookiejar,urllib.request

　　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)

第二种保存cookie方式

import http.cookiejar,urllib.request

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)

读取cookie

import http.cookiejar,urllib.request

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'))

六、异常处理

# 例1：
from urllib import reqeust,error

try:
    response =request.urlopen('http://cuiqingcai.com/index.htm')　
except error.URLError as e:
    print(e.reason)　　# url异常捕获

# 例2:
from urllib import reqeust,error

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

七、URL解析

urlparse # url 拆分

urllib.parse.urlparse(urlstring,scheme='',allow_fragments=True)

# 例1：
from urllib.parse import urlparse    # url 拆分

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

# 例2：
from urllib.parse import urlparse   # 没有http

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

 # 例3：
from urllib.parse import urlparse

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

例4：

from urllib.parse import urlparse

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

# 例5：

from urllib.parse import urlparse

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

拼接：urlunparse

例子：

from urllib.parse import urlunparse

data=['http','www.baidu.com','index.html','user','a=6','comment']
print(urlunparse(data))

urljoin


from urllib.parse import urljoin
print(urljoin('http://www.baidu.com','FAQ.html'))
 # 后面覆盖前面的

urlencode

from urllib.parse import urlencode

params={
    'name':'gemey',
    'age':22
}
base_url='http//www.baidu.com?'
url = base_url+urlencode(params)
print(url)
http://www.baidu.com?name=gemey&age=22

example:

urllib是Python自带的标准库，无需安装，直接可以用。
提供了如下功能：
网页请求
响应获取
代理和cookie设置
异常处理
URL解析
爬虫所需要的功能，基本上在urllib中都能找到，学习这个标准库，可以更加深入的理解后面更加便利的requests库。

urllib库
urlopen 语法

urllib.request.urlopen(url,data=None,[timeout,]*,cafile=None,capath=None,cadefault=False,context=None)
# url:访问的网址
# data:额外的数据，如header，form data
# 用法:
# request:GET
import urllib.request
response = urllib.request.urlopen('http://www.baidu.com')
print(response.read().decode('utf-8'))

# request: POST
# http测试：http://httpbin.org/
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())

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

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')

解析

# 主要是一个工具模块，可用于为爬虫提供URL。
# urlparse:拆分URL
urlib.parse.urlparse(urlstring,scheme='', allow_fragments=True)
# scheme: 协议类型
# 是否忽略'#'部分
# 举个例子

from urllib import urlparse
result = urlparse("https://edu.hellobi.com/course/157/play/lesson/2580")
result
##ParseResult(scheme='https', netloc='edu.hellobi.com', path='/course/157/play/lesson/2580', params='', query='', fragment='')
urlunparse:拼接URL，为urlparse的反向操作

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

# urljoin:拼接两个URL
# urljoin
# urlencode:字典对象转换成GET请求对象

from urllib.parse import urlencode
params = {
    'name':'germey',
    'age': 22
}
base_url = 'http://www.baidu.com?'
url = base_url + urlencode(params)
print(url)

八、响应

# 响应类型
import urllib.open
response = urllib.request.urlopen('https:///www.python.org')
print(type(response))
# 状态码， 响应头
import urllib.request
response = urllib.request.urlopen('https://www.python.org')
print(response.status)
print(response.getheaders())
print(response.getheader('Server'))
Request
声明一个request对象，该对象可以包括header等信息，然后用urlopen打开。

# 简单例子
import urllib.request
request = urllib.request.Requests('https://python.org')
response = urllib.request.urlopen(request)
print(response.read().decode('utf-8'))

# 增加header
from urllib import request, parse
url = 'http://httpbin.org/post'
headers = {
    'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36'
    'Host':'httpbin.org'
}
# 构造POST表格
dict = {
    'name':'Germey'
}
data = bytes(parse.urlencode(dict),encoding='utf8')
req = request.Request(url=url,data=data,headers=headers,method='POST')
response = request.urlopen(req)
print(response.read()).decode('utf-8')
# 或者随后增加header
from urllib import request, parse
url = 'http://httpbin.org/post'
dict = {
    'name':'Germey'
}
req = request.Request(url=url,data=data,method='POST')
req.add_hader('User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36')
response = request.urlopen(req)
print(response.read().decode('utf-8'))

九、代理

import urllib.request
proxy_handler = urllib.request.ProxyHandler({
    'http':'http://127.0.0.1:9743'
    'https':'https://127.0.0.1.9743'
})
opener = urllib.request.build_openner(proxy_handler)
response = opener.open('http://www.baidu.com')
print(response.read())
Cookie:客户端用于记录用户身份,维持登录信息

import http.cookiejar, urllib.request

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)

# 保存cooki为文本
import http.cookiejar, urllib.request
filename = "cookie.txt"
# 保存类型有很多种
# 类型1
cookie = http.cookiejar.MozillaCookieJar(filename)
# 类型2
cookie = http.cookiejar.LWPCookieJar(filename)

handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(handler)
response = opener.open("http://www.baidu.com")

# 使用相应的方法读取
import http.cookiejar, urllib.request
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")

十、异常处理

# 捕获异常，保证程序稳定运行

# 访问不存在的页面
from urllib import request, error
try:
    response = request.urlopen('http://cuiqingcai.com/index.htm')
except error.URLError as e:
    print(e.reason)

# 先捕获子类错误
from urllib imort 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")

# 判断原因
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')