python爬虫入门（1）-urllib模块

作用：用于读取来自网上(服务器上)的数据

基本方法：urllib.request.urlopen(url,data=None,[]timeout]*,cafile=None,cadefault=False,context=None)

• url:需要打开的网址
• data:Post提交的数据
• timeout:设置网站的访问超时时间

示例1：获取页面

import urllib.request

response = urllib.request.urlopen("http://www.fishc.com")#是一个HTTP响应类型
html =response.read()#读取响应内容，为bytes类型
# print(type(html),html)     #输出的为一串<class ‘bytes‘>
html = html.decode(‘utf-8‘)#bytes类型解码为str类型
print(html)

示例2：抓一只猫

import urllib.request

response = urllib.request.urlopen("http://placekitten.com/g/400/400")
cat_img = response.read()

with open(‘cat_400_400.jpg‘, ‘wb‘) as f:
    f.write(cat_img)

示例3：翻译器

右击浏览器，选择检查或审查元素，再点击网络，找到post的 Name，复制RequestURL

在headers中找到Form Data,复制表单中内容

import urllib.request
import urllib.parse
import json
import time

while True:

    content = input("请输入需要翻译的内容《输入q!退出程序》：")
    if content == ‘q!‘:
        break

    url = "http://fanyi.youdao.com/translate?smartresult=dict&smartresult=rule&smartresult=ugc&sessionFrom=http://www.youdao.com/"    #即RequestURL中的链接
    data = {}
    #Form Data中的内容，适当删除无用信息
    data[‘i‘] = content
    data[‘smartresult‘] = ‘dict‘
    data[‘client‘] = ‘fanyideskweb‘
    data[‘doctype‘] = ‘json‘
    data[‘version‘] = ‘2.1‘
    data[‘keyfrom‘] = ‘fanyi.web‘
    data[‘action‘] = ‘FY_BY_CLICKBUTTON‘
    data[‘typoResult‘] = ‘true‘
    data = urllib.parse.urlencode(data).encode(‘utf-8‘)
    #打开网址并提交表单
    response = urllib.request.urlopen(url, data)
    html = response.read().decode(‘utf-8‘)
    target = json.loads(html)

    print("翻译结果：%s" % (target[‘translateResult‘][0][0][‘tgt‘]))
    time.sleep(2)

隐藏和代理

隐藏：1.通过request的headers参数修改

2.通过Request.add_header()方法修改

代理：1.proxy_support = urllib.request.ProxyHandler({}) #参数是一个字典{‘类型‘：‘代理IP:端口号‘}

2.opener = urllib.request.build_opener(proxy_support) #定制、创建一个opener

3.urllib.request.install_opener(opener) #安装opener

opener.open(url) #调用opener

代理

示例5：代理

import urllib.request
import random

url = ‘http://www.whatismyip.com.tw/‘
iplist = [‘61.191.41.130:80‘,‘115.46.97.122:8123‘,]

#参数是一个字典{‘类型‘：‘代理IP：端口号‘}
proxy_support = urllib.request.ProxyHandler({‘http‘:random.choice(iplist)})
#定制、创建一个opener
opener = urllib.request.build_opener(proxy_support)
#通过addheaders修改User-Agent
opener.addheaders = [(‘User-Agent‘,‘Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.97 Safari/537.36‘)]
#安装opener
urllib.request.install_opener(opener)

response = urllib.request.urlopen(url)
html = response.read().decode(‘utf-8‘)

print(html)

示例6：简单爬取贴吧图片

import urllib.request
import re

def open_url(url):
    #打开URL并修改header，将URL内容读取
    req = urllib.request.Request(url)
    #通过add_header修改User-Agent
    req.add_header(‘User-Agent‘,‘Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.97 Safari/537.36‘)
    page = urllib.request.urlopen(req)
    html = page.read().decode(‘utf-8‘)

    return html


def get_img(html):
    p = r‘<img class="BDE_Image" src="([^"]+\.jpg)‘
    imglist = re.findall(p,html)#寻找到图片的链接

    for each in imglist:
        filename = each.split("/")[-1]
        urllib.request.urlretrieve(each,filename,None)#保存图片

if __name__ == ‘__main__‘:
    url = "https://tieba.baidu.com/p/5090206152"
    get_img(open_url(url))

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