python3 implements N methods of crawling web resources

In the past two days, I have learned the methods of grabbing web resources by python3 and found many methods. Therefore, I will add 1 small note today.

1. Easiest

import urllib.request
response = urllib.request.urlopen('http://python.org/')
html = response.read() 

2. Use Request

import urllib.request
 
req = urllib.request.Request('http://python.org/')
response = urllib.request.urlopen(req)
the_page = response.read()

3. Send data

#! /usr/bin/env python3
 
import urllib.parse
import urllib.request
 
url = 'http://localhost/login.php'
user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'
values = {
     'act' : 'login',
     'login[email]' : 'yzhang@i9i8.com',
     'login[password]' : '123456'
     }
 
data = urllib.parse.urlencode(values)
req = urllib.request.Request(url, data)
req.add_header('Referer', 'http://www.python.org/')
response = urllib.request.urlopen(req)
the_page = response.read()
 
print(the_page.decode("utf8"))

4. Send data and header

#! /usr/bin/env python3
 
import urllib.parse
import urllib.request
 
url = 'http://localhost/login.php'
user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'
values = {
     'act' : 'login',
     'login[email]' : 'yzhang@i9i8.com',
     'login[password]' : '123456'
     }
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()
 
print(the_page.decode("utf8"))

5. http error

#! /usr/bin/env python3
 
import urllib.request
 
req = urllib.request.Request('http://www.python.org/fish.html')
try:
  urllib.request.urlopen(req)
except urllib.error.HTTPError as e:
  print(e.code)
  print(e.read().decode("utf8"))

6. Exception handling 1

#! /usr/bin/env python3
 
from urllib.request import Request, urlopen
from urllib.error import URLError, HTTPError
req = Request("http://twitter.com/")
try:
  response = urlopen(req)
except HTTPError as e:
  print('The server couldn\'t fulfill the request.')
  print('Error code: ', e.code)
except URLError as e:
  print('We failed to reach a server.')
  print('Reason: ', e.reason)
else:
  print("good!")
  print(response.read().decode("utf8"))

7. Exception handling 2

#! /usr/bin/env python3
 
from urllib.request import Request, urlopen
from urllib.error import URLError
req = Request("http://twitter.com/")
try:
  response = urlopen(req)
except URLError as e:
  if hasattr(e, 'reason'):
    print('We failed to reach a server.')
    print('Reason: ', e.reason)
  elif hasattr(e, 'code'):
    print('The server couldn\'t fulfill the request.')
    print('Error code: ', e.code)
else:
  print("good!")
  print(response.read().decode("utf8"))

8. HTTP certification

#! /usr/bin/env python3
 
import urllib.request
 
# create a password manager
password_mgr = urllib.request.HTTPPasswordMgrWithDefaultRealm()
 
# Add the username and password.
# If we knew the realm, we could use it instead of None.
top_level_url = "https://cms.tetx.com/"
password_mgr.add_password(None, top_level_url, 'yzhang', 'cccddd')
 
handler = urllib.request.HTTPBasicAuthHandler(password_mgr)
 
# create "opener" (OpenerDirector instance)
opener = urllib.request.build_opener(handler)
 
# use the opener to fetch a URL
a_url = "https://cms.tetx.com/"
x = opener.open(a_url)
print(x.read())
 
# Install the opener.
# Now all calls to urllib.request.urlopen use our opener.
urllib.request.install_opener(opener)
 
a = urllib.request.urlopen(a_url).read().decode('utf8')
print(a)

9. Use agents

#! /usr/bin/env python3
 
import urllib.request
 
proxy_support = urllib.request.ProxyHandler({'sock5': 'localhost:1080'})
opener = urllib.request.build_opener(proxy_support)
urllib.request.install_opener(opener)

 
a = urllib.request.urlopen("http://g.cn").read().decode("utf8")
print(a)

10, timeout

#! /usr/bin/env python3
 
import socket
import urllib.request
 
# timeout in seconds
timeout = 2
socket.setdefaulttimeout(timeout)
 
# this call to urllib.request.urlopen now uses the default timeout
# we have set in the socket module
req = urllib.request.Request('http://twitter.com/')
a = urllib.request.urlopen(req).read()
print(a)