urllib提供了一系列用于操作URL的功能

Get

urllib的request模塊可以非常方便的抓取URL的內容, 也就是發送一個GET請求到制定的頁面, 然后返回HTTP的響應:

例如, 對豆瓣的一個URLhttps://api.douban.com/v2/book/2129650進行抓取, 并返回響應:

from urllib import request

with request.urlopen('https://api.douban.com/v2/book/2129650') as f:

data = f.read()

print('Status:', f.status, f.reason)

for k, v in f.getheaders():

print('%s: %s' % (k, v))

print('Data:', data.decode('utf-8'))

可以看到HTTP響應的頭和JSON數據：

Status: 200 OK

Server: nginx

Date: Tue, 26 May 2015 10:02:27 GMT

Content-Type: application/json; charset=utf-8

Content-Length: 2049

Connection: close

Expires: Sun, 1 Jan 2006 01:00:00 GMT

Pragma: no-cache

Cache-Control: must-revalidate, no-cache, private

X-DAE-Node: pidl1

Data: {"rating":{"max":10,"numRaters":16,"average":"7.4","min":0},"subtitle":"","author":["廖雪峰編著"],"pubdate":"2007-6",...}

如果我們要想模擬瀏覽器發送GET請求，就需要使用Request對象，通過往Request對象添加HTTP頭，我們就可以把請求偽裝成瀏覽器。例如，模擬iPhone 6去請求豆瓣首頁：

from urllib import request

req = request.Request('http://www.douban.com/')

req.add_header('User-Agent', 'Mozilla/6.0 (iPhone; CPU iPhone OS 8_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/8.0 Mobile/10A5376e Safari/8536.25')

with request.urlopen(req) as f:

print('Status:', f.status, f.reason)

for k, v in f.getheaders():

print('%s: %s' % (k, v))

print('Data:', f.read().decode('utf-8'))

這樣豆瓣會返回適合iPhone的移動版網頁：

...

...

Post

如果要以POST發送一個請求，只需要把參數data以bytes形式傳入。

我們模擬一個微博登錄，先讀取登錄的郵箱和口令，然后按照weibo.cn的登錄頁的格式以username=xxx&password=xxx的編碼傳入

from urllib import request, parse

print('Login to weibo.cn...')

email = input('Email: ')

passwd = input('Password: ')

login_data = parse.urlencode([

('username', email),

('password', passwd),

('entry', 'mweibo'),

('client_id', ''),

('savestate', '1'),

('ec', ''),

('pagerefer', 'https://passport.weibo.cn/signin/welcome?entry=mweibo&r=http%3A%2F%2Fm.weibo.cn%2F')

])

req = request.Request('https://passport.weibo.cn/sso/login')

req.add_header('Origin', 'https://passport.weibo.cn')

req.add_header('User-Agent', 'Mozilla/6.0 (iPhone; CPU iPhone OS 8_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/8.0 Mobile/10A5376e Safari/8536.25')

req.add_header('Referer', 'https://passport.weibo.cn/signin/login?entry=mweibo&res=wel&wm=3349&r=http%3A%2F%2Fm.weibo.cn%2F')

with request.urlopen(req, data=login_data.encode('utf-8')) as f:

print('Status:', f.status, f.reason)

for k, v in f.getheaders():

print('%s: %s' % (k, v))

print('Data:', f.read().decode('utf-8'))

如果登錄成功，我們獲得的響應如下：

Status: 200 OK

Server: nginx/1.2.0

...

Set-Cookie: SSOLoginState=1432620126; path=/; domain=weibo.cn

...

Data: {"retcode":20000000,"msg":"","data":{...,"uid":"1658384301"}}

如果登錄失敗，我們獲得的響應如下：

...

Data: {"retcode":50011015,"msg":"\u7528\u6237\u540d\u6216\u5bc6\u7801\u9519\u8bef","data":{"username":"example@python.org","errline":536}}

利用urllib讀取JSON，然后將JSON解析為Python對象：

import json

def fetch_data(url):

return json.load(request.urlopen(url))