爬蟲第三講：基本的urllib庫

Urllib庫是python內置的庫

什么是Urllib

1.urllib.request 請求模塊
2.urllib.error 異常處理模塊
3.urllib.parse url解析模塊
4.urllib.robotparser robots.txt解析模塊

用法

  • urlopen

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

    GET類型的請求

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

    POST類型的請求

    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())

    帶超時參數

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

    測試較短的超時參數

    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('TIMEOUT')
else:
  print('It is OK!')

    查看urlopen返回值的類型

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

    輸出結果:<class 'http.client.HTTPResponse'>

響應內容--狀態碼和響應頭

import urllib.request
response = urllib.request.urlopen('https://www.python.org')
print(response.status)
print(response.getheaders())
print(response.getheader('Server'))
print(response.read().decode('utf-8'))  #響應體，用utf-8解碼

輸出結果：
200
[('Server', 'nginx'), ('Content-Type', 'text/html; charset=utf-8'), ('X-Frame-Options', 'SAMEORIGIN'), ('x-xss-protection', '1; mode=block'), ('X-Clacks-Overhead', 'GNU Terry Pratchett'), ('Via', '1.1 varnish'), ('Content-Length', '48809'), ('Accept-Ranges', 'bytes'), ('Date', 'Sat, 18 Aug 2018 12:56:38 GMT'), ('Via', '1.1 varnish'), ('Age', '129'), ('Connection', 'close'), ('X-Served-By', 'cache-iad2128-IAD, cache-nrt6150-NRT'), ('X-Cache', 'HIT, HIT'), ('X-Cache-Hits', '2, 48'), ('X-Timer', 'S1534596999.663138,VS0,VE0'), ('Vary', 'Cookie'), ('Strict-Transport-Security', 'max-age=63072000; includeSubDomains')]
nginx

  • request方法

如果使用復雜的請求可以在urlopen方法中使用request參數，通過構造request參數可以方便的設定請求的方式。

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

輸出結果就是請求https://python.org的響應體。
使用POST方法發送請求，并用request構造函數構造request，作為參數調用urlopen

from urllib import request,parse
url = 'http://httpbin.org/post'
headers = {
      'User-Agent':'Mozilla/4.0(bompatible;MSIE 5.5;Windows NT)',
      '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'))

依然是使用POST方法發送請求，用Request構造函數構造request，作為參數傳遞給urlopen，但request中的headers不在構造函數中指定，而在使用request.add_header添加header。如果有很多鍵值對要傳遞，可以用for循環多次調用add_header

from urllib import request,parse
url = 'http://httpbin.org/post'
dict = {
      'name':'XieZ'
      }
data = bytes(parse.urlencode(dict),encoding='utf8')
req = request.Request(url=url,data=data,method='POST')
req.add_header('User-Agent','Mozilla/4.0(compatible;MSIE 5.5;Windows NT)')
response = request.urlopen(req)
print(response.read().decode('utf-8'))

handler -- urllib中的高級用法，代理、cookie等等各種高級功能都是各種handler實現的。

  • 代理

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

  • Cookie--Cookie可以用來保存登錄會話信息

    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)

    把Cookie保存至文件，方便將來爬蟲使用cookie登錄網站，保持登錄狀態

    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)

    這樣Cookie就保存在文件中了，MozillaCookieJar是cookiejar的子類，是火狐瀏覽器的cookie保存格式，還有其他的cookie保存格式，比如LWPCookieJar。在使用時，用什么格式保存就用什么格式讀取cookie就行

    使用LWPCookieJar將cookie保存到文件，并且讀取此文件中的cookie，并請求頁面

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

  • urllib的異常處理模塊

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

    結果顯示：[Errno -2] Name or service not known

    HTTPError含有reason、code、headers屬性

    from urllib import request,error
try:
  response = request.urlopen('http://www.sina.com.cn/99999.html')
except error.HTTPError as e:
  print(e.reason,e.code,e.headers,sep='\n')
  print('This is end of HTTPError\n')
except error.URLError as e:
  print(e.reason)
else:
  print('Request Sucessfully')

    結果顯示：
Not Found
404
Server: nginx
Date: Sun, 19 Aug 2018 22:06:25 GMT
Content-Type: text/html
Transfer-Encoding: chunked
Connection: close
Vary: Accept-Encoding
Age: 0
Via: http/1.1 ctc.nanjing.ha2ts4.77 (ApacheTrafficServer/6.2.1 [cMsSf ])
X-Cache: MISS.77
X-Via-CDN:     f=edge,s=ctc.nanjing.ha2ts4.65.nb.sinaedge.com,c=61.171.236.224;f=Edge,s=ctc.nanjing.ha2ts4.77,c=202.102.94.65
X-Via-Edge: 1534716385494e0ecab3d7c5e66ca3150b8e6


This is end of HTTPError

  • URL解析模塊--urlparse和urlunparse
    1.urlparse函數

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

    *返回結果：<class 'urllib.parse.ParseResult'> ParseResult(scheme='http', netloc='www.baidu.com', path='/index.html', params='user', query='id=5', fragment='comment')

2.urlunparse函數

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

*返回結果：http://www.baidu.com/index.html;user?a=6#comment
urlunparse就是urlparse的反函數，把各種參數拼接為一個url
3.urljpin函數

from urllib.parse import urljoin
print(urljoin('http://www.baidu.com','FAQ.html'))
print(urljoin('http://www.baidu.com','https://lllll.com/FAQ.html'))

*返回結果:http://www.baidu.com/FAQ.html
https://lllll.com/FAQ.html
4.urlencode--可以把字典對象轉換成get請求參數，很常用

from urllib.parse import urlencode
params = {
      'name':'xiezheng',
      'age':23
      }
base_url = 'http://www.baidu.com?'
url = base_url + urlencode(params)
print(url)

*返回結果:http://www.baidu.com?name=xiezheng&age=23

  • urllib.robotparser模塊，用來解析robot.txt文件
最后編輯于 ：
?著作權歸作者所有,轉載或內容合作請聯系作者
平臺聲明：文章內容（如有圖片或視頻亦包括在內）由作者上傳并發布，文章內容僅代表作者本人觀點，簡書系信息發布平臺，僅提供信息存儲服務。

推薦閱讀更多精彩內容