Python3.X 抓取网络资源

Python 3.X 要使用urllib.request 来抓取网络资源。

最简单的方式：

#coding=utf-8
import urllib.request
response = urllib.request.urlopen('http://python.org/')
buff = response.read()
#显示
html = buff.decode("utf8")
response.close()
print(html)

使用Request的方式：

#coding=utf-8
import urllib.request
req = urllib.request.Request('http://www.voidspace.org.uk')
response = urllib.request.urlopen(req)
buff = response.read()
#显示
the_page = buff.decode("utf8")
response.close()
print(the_page)

这种方式同样可以用来处理其他URL，例如FTP：

#coding=utf-8
import urllib.request
req = urllib.request.Request('ftp://ftp.pku.edu.cn/')
response = urllib.request.urlopen(req)
buff = response.read()
#显示
the_page = buff.decode("utf8")
response.close()
print(the_page)

使用POST请求：

import urllib.parseimport
urllib.requesturl = 'http://www.someserver.com/cgi-bin/register.cgi'
values = {'name' : 'Michael Foord',
'location' : 'Northampton',
'language' : 'Python' }

data = urllib.parse.urlencode(values)
req = urllib.request.Request(url, data)
response = urllib.request.urlopen(req)
the_page = response.read()

使用GET请求：

import urllib.request
import urllib.parse
data = {}
data['name'] = 'Somebody Here'
data['location'] = 'Northampton'
data['language'] = 'Python'
url_values = urllib.parse.urlencode(data)
print(url_values)
name=Somebody+Here&language=Python&location=Northampton
url = 'http://www.example.com/example.cgi'
full_url = url + '?' + url_values
data = urllib.request.open(full_url)

添加header：

import urllib.parse
import urllib.request

url = 'http://www.someserver.com/cgi-bin/register.cgi'
user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'
values = {'name' : 'Michael Foord',
'location' : 'Northampton',
'language' : 'Python' }
headers = { 'User-Agent' : user_agent }

data = urllib.parse.urlencode(values)
req = urllib.request.Request(url, data, headers)
response = urllib.request.urlopen(req)
the_page = response.read()

错误处理：

req = urllib.request.Request('http://www.pretend_server.org')
try: urllib.request.urlopen(req)
except urllib.error.URLError as e:
print(e.reason)

返回的错误代码：

# Table mapping response codes to messages; entries have the
# form {code: (shortmessage, longmessage)}.
responses = {
100: ('Continue', 'Request received, please continue'),
101: ('Switching Protocols',
'Switching to new protocol; obey Upgrade header'),

200: ('OK', 'Request fulfilled, document follows'),
201: ('Created', 'Document created, URL follows'),
202: ('Accepted',
'Request accepted, processing continues off-line'),
203: ('Non-Authoritative Information', 'Request fulfilled from cache'),
204: ('No Content', 'Request fulfilled, nothing follows'),
205: ('Reset Content', 'Clear input form for further input.'),
206: ('Partial Content', 'Partial content follows.'),

300: ('Multiple Choices',
'Object has several resources -- see URI list'),
301: ('Moved Permanently', 'Object moved permanently -- see URI list'),
302: ('Found', 'Object moved temporarily -- see URI list'),
303: ('See Other', 'Object moved -- see Method and URL list'),
304: ('Not Modified',
'Document has not changed since given time'),
305: ('Use Proxy',
'You must use proxy specified in Location to access this '
'resource.'),
307: ('Temporary Redirect',
'Object moved temporarily -- see URI list'),

400: ('Bad Request',
'Bad request syntax or unsupported method'),
401: ('Unauthorized',
'No permission -- see authorization schemes'),
402: ('Payment Required',
'No payment -- see charging schemes'),
403: ('Forbidden',
'Request forbidden -- authorization will not help'),
404: ('Not Found', 'Nothing matches the given URI'),
405: ('Method Not Allowed',
'Specified method is invalid for this server.'),
406: ('Not Acceptable', 'URI not available in preferred format.'),
407: ('Proxy Authentication Required', 'You must authenticate with '
'this proxy before proceeding.'),
408: ('Request Timeout', 'Request timed out; try again later.'),
409: ('Conflict', 'Request conflict.'),
410: ('Gone',
'URI no longer exists and has been permanently removed.'),
411: ('Length Required', 'Client must specify Content-Length.'),
412: ('Precondition Failed', 'Precondition in headers is false.'),
413: ('Request Entity Too Large', 'Entity is too large.'),
414: ('Request-URI Too Long', 'URI is too long.'),
415: ('Unsupported Media Type', 'Entity body in unsupported format.'),
416: ('Requested Range Not Satisfiable',
'Cannot satisfy request range.'),
417: ('Expectation Failed',
'Expect condition could not be satisfied.'),

500: ('Internal Server Error', 'Server got itself in trouble'),
501: ('Not Implemented',
'Server does not support this operation'),
502: ('Bad Gateway', 'Invalid responses from another server/proxy.'),
503: ('Service Unavailable',
'The server cannot process the request due to a high load'),
504: ('Gateway Timeout',
'The gateway server did not receive a timely response'),
505: ('HTTP Version Not Supported', 'Cannot fulfill request.'),
}