一 pycurl介绍

pycurl模块为libcurl库提供了一个python接口。libcurl是一个开源免费且方便快捷的基于客户端的url传输库，支持FTP,HTTP,HTTPS,IMAP,IMAPS,LDAP,LDAPS,POP3,POP3S,RTMP,RTSP,SCP等等。libcurl还支持SSL认证，HTTP POST,HTTP PUT,FTP UPLOADING等等。和urllib模块类似，pycurl模块也可以用来获取一个url的对象。pycurl使用了大部分libcurl提供的函数，使得pycurl具有以下特性：

快速  libcurl本身就很快速，pycurl就是对libcurl进行了一次封装，所以pycurl同样很快速。

支持多种协议，SSL,认证和代理选项。pycurl支持大部分libcurl的回调函数。

multi 和 share 接口支持

可以和应用的I/O整合

二 pycurl使用案例

1.安装pycurl

CentOS6 下使用pip install pycurl安装

可以使用ipython来调试

2.获取一个url响应结果

import pycurl

from StringIO import StringIO

buffer=StringIO()

c=pycurl.Curl()

c.setopt(c.URL,'http://pycurl.io/')

c.setopt(c.WRITEFUNCTION,buffer.write)

c.perform()

c.close()

body=buffer.getvalue()

print(body)

　　

pycurl本身不会存储url的响应结果，因此，需要设置一个buffer，让pycurl将结果写入到这个buffer中

想要获取调试信息，可以设置

c.setopt(c.VERBOSE, True)

　　

 

等同于 curl -v

3.审查响应头

在实际案例中，我们想要根据服务端的编码格式来解码响应结果

import pycurl

import re

try:

   from io import BytesIO

except ImportError:

   from StringIO import StringIO as BytesIO

headers={}

def header_function(header_line):

    # HTTP standard specifies that headers are encoded in iso-8859-1.

    # On Python 2, decoding step can be skipped.

    # On Python 3, decoding step is required.

    header_line=header_line.decode('iso-8859-1')

    # Header lines include the first status line (HTTP/1.x ...).

    # We are going to ignore all lines that don't have a colon in them.

    # This will botch headers that are split on multiple lines...

    if ':' not in header_line:

        return

    # Break the header line into header name and value.

    name, value = header_line.split(':', 1)

    # Remove whitespace that may be present.

    # Header lines include the trailing newline, and there may be whitespace

    # around the colon.

    name = name.strip()

    value = value.strip()

    # Header names are case insensitive.

    # Lowercase name here.

    name = name.lower()

    # Now we can actually record the header name and value.

    headers[name] = value

buffer=BytesIO()

c=pycurl.Curl()

c.setopt(c.URL,'http://pycurl.io')

c.setopt(c.WRITEFUNCTION,buffer.write)

#set our header function

c.setopt(c.HEADERFUNCTION,header_function)

c.perform()

c.close()

# Figure out what encoding was sent with the response, if any.

# Check against lowercased header name.

encoding=None

if 'content-type' in headers:

    content_type=headers['content-type'].lower()

    match=re.search('charset=(\S+)', content_type)

    if match:

        encoding=match.group(1)

        print('Decoding using %s' % encoding)

if encoding is None:

    # Default encoding for HTML is iso-8859-1.

    # Other content types may have different default encoding,

    # or in case of binary data, may have no encoding at all.

    encoding='iso-8859-1'

    print('Assuming encoding is %s' % encoding)

body=buffer.getvalue()

# Decode using the encoding we figured out.

print(body.decode(encoding))

　　

 
 

4.将响应结果写入到文件

import pycurl

with open('out.html','wb') as f:

   c=pycurl.Curl()

   c.setopt(c.URL,'http://pycurl.io/')

   c.setopt(c.WRITEDATA,f)

   c.perform()

   c.close()

　　

 

这里最重要的部分就是以二进制模式打开文件，这样响应结果可以以字节码写入到文件中，不需要编码和解码。

5.跟踪url跳转

libcurl和pycurl默认不跟踪url跳转。

import pycurl

c=pycurl.Curl()

#Redirects to https://www.python.org/.

c.setopt(c.URL,'http://www.python.org/')

#Follow redirect

c.setopt(c.FOLLOWLOCATION,True)

c.perform()

c.close()

　　

 

6.审查响应

import pycurl

try:

    from io import BytesIO

except ImportError:

    from StringIO import StringIO as BytesIO

buffer=BytesIO()

c=pycurl.Curl()

c.setopt(c.URL,'http://www.python.org/')

c.setopt(c.WRITEFUNCTION,buffer.write)

c.perform()

#Last used URL

print('Effective_url: %s' %c.getinfo(c.EFFECTIVE_URL))

#HTTP response code

print('Response_code: %d' %c.getinfo(c.RESPONSE_CODE))

#Total time of previous transfer

print('Total_time: %f' %c.getinfo(c.TOTAL_TIME))

#Time from start until name resolving completed

print('Namelookup_time: %f' %c.getinfo(c.NAMELOOKUP_TIME))

#Time from start until remote host or proxy completed

print('Connect_time: %f' %c.getinfo(c.CONNECT_TIME))

#Time from start until SLL/SSH handshake completed

print('SSL/SSH_time: %f' %c.getinfo(c.APPCONNECT_TIME))

#Time from start until just before the transfer begins

print('Pretransfer_time: %f' %c.getinfo(c.PRETRANSFER_TIME))

#Time from start until just when the first byte is received

print('Starttransfer_time: %f' %c.getinfo(c.STARTTRANSFER_TIME))

#Time taken for all redirect steps before the final transfer

print('Redirect_time: %f' %c.getinfo(c.REDIRECT_TIME))

#Total number of redirects that were followed

print('Redirect_count: %d' %c.getinfo(c.REDIRECT_COUNT))

#URL a redirect would take you to,had you enabled redirects

print('Redirect_url: %s' %c.getinfo(c.REDIRECT_URL))

#Number of bytes uploaded

print('Size_upload: %d' %c.getinfo(c.SIZE_UPLOAD))

#Average upload speed

print('Speed_upload: %f' %c.getinfo(c.SPEED_UPLOAD))

#Number of bytes downloaded

print('Size_download: %d' %c.getinfo(c.SIZE_DOWNLOAD))

#Average download speed

print('Speed_download: %f' %c.getinfo(c.SPEED_DOWNLOAD))

#getinfo must be called before close

c.close()

　　

# python response_info.py

Effective_url: http://www.python.org/

Response_code: 301

Total_time: 0.105395

Namelookup_time: 0.051208

Connect_time: 0.078317

SSL/SSH_time: 0.000000

Pretransfer_time: 0.078322

Starttransfer_time: 0.105297

Redirect_time: 0.000000

Redirect_count: 0

Redirect_url: https://www.python.org/

Size_upload: 0

Speed_upload: 0.000000

Size_download: 0

Speed_download: 0.000000

　　

 
 
 
 

7.发送表单数据

发送表单数据使用POSTFIELDS参数

import pycurl

try:

  #python 3

  from urllib.parse import urlencode

except ImportError:

  from urllib import urlencode

c=pycurl.Curl()

c.setopt(c.URL,'http://pycurl.io/tests/testpostvars.php')

post_data={'field':'value'}

#Form data must be provided already urlencoded

postfields=urlencode(post_data)

# Sets request method to POST,

# Content-Type header to application/x-www-form-urlencoded

# and data to send in request body.

c.setopt(c.POSTFIELDS, postfields)

c.perform()

c.close()

　　

 

8.文件上传

上传文件使用HTTPPOST参数，上传一个物理文件，使用FORM_FILE

import pycurl

c = pycurl.Curl()

c.setopt(c.URL, 'http://pycurl.io/tests/testfileupload.php')

c.setopt(c.HTTPPOST, [

    ('fileupload', (

        # upload the contents of this file

        c.FORM_FILE, __file__,

    )),

])

c.perform()

c.close()

　　

 

为上传的文件设置不同的文件名和内容类型

import pycurl

c = pycurl.Curl()

c.setopt(c.URL, 'http://pycurl.io/tests/testfileupload.php')

c.setopt(c.HTTPPOST, [

    ('fileupload', (

        # upload the contents of this file

        c.FORM_FILE, __file__,

        # specify a different file name for the upload

        c.FORM_FILENAME, 'helloworld.py',

        # specify a different content type

        c.FORM_CONTENTTYPE, 'application/x-python',

    )),

])

c.perform()

c.close()

　　

 
 

如果文件数据在内存中，使用BUFFER/BUFFERPTR

import pycurl

c = pycurl.Curl()

c.setopt(c.URL, 'http://pycurl.io/tests/testfileupload.php')

c.setopt(c.HTTPPOST, [

    ('fileupload', (

        c.FORM_BUFFER, 'readme.txt',

        c.FORM_BUFFERPTR, 'This is a fancy readme file',

    )),

])

c.perform()

c.close()

　　

 

9.处理FTP协议

import pycurl

c = pycurl.Curl()

c.setopt(c.URL, 'ftp://ftp.sunet.se/')

c.setopt(c.FTP_USE_EPSV, 1)

c.setopt(c.QUOTE, ['cwd pub', 'type i'])

c.perform()

c.close()

　　

 

10.Sharing Data 

import pycurl

import threading

print >>sys.stderr, 'Testing', pycurl.version

class Test(threading.Thread):

    def __init__(self, share):

        threading.Thread.__init__(self)

        self.curl = pycurl.Curl()

        self.curl.setopt(pycurl.URL, 'http://curl.haxx.se')

        self.curl.setopt(pycurl.SHARE, share)

    def run(self):

        self.curl.perform()

        self.curl.close()

s = pycurl.CurlShare()

s.setopt(pycurl.SH_SHARE, pycurl.LOCK_DATA_COOKIE)

s.setopt(pycurl.SH_SHARE, pycurl.LOCK_DATA_DNS)

t1 = Test(s)

t2 = Test(s)

t1.start()

t2.start()

del s

　　

 

11.使用multi接口

libcurl的easy接口是一个同步的，高效的，上手快的用于文件传输的接口。multi接口是一个异步的接口，它可以使用一个或者多个线程进行多路传输。

multi接口比easy接口多了以下几个功能：

提供一个pull接口。使用libcurl的应用决定哪里何时询问libcurl去接收或者发送数据

在同一个线程中启动多路同步传输而不必使应用程序变得更复杂

使得应用程序同时等待在应用程序本身的文件描述符和libcurl文件描述符上的动作变得简单许多

使得基于事件处理和扩展的传输可以达到上千个并行连接

 

例1

import pycurl

m = pycurl.CurlMulti()

m.handles = []

c1 = pycurl.Curl()

c2 = pycurl.Curl()

c1.setopt(c1.URL, 'http://curl.haxx.se')

c2.setopt(c2.URL, 'http://cnn.com')

c2.setopt(c2.FOLLOWLOCATION, 1)

m.add_handle(c1)

m.add_handle(c2)

m.handles.append(c1)

m.handles.append(c2)

num_handles = len(m.handles)

while num_handles:

    while 1:

        ret, num_handles = m.perform()

        if ret != pycurl.E_CALL_MULTI_PERFORM:

            break

    m.select(1.0)

m.remove_handle(c2)

m.remove_handle(c1)

del m.handles

m.close()

c1.close()

c2.close()

　　

 

 
 

例2

import os, sys

try:

    from cStringIO import StringIO

except ImportError:

    from StringIO import StringIO

import pycurl

urls = (

    "http://curl.haxx.se",

    "http://www.python.org",

    "http://pycurl.sourceforge.net",

    "http://pycurl.sourceforge.net/tests/403_FORBIDDEN",  # that actually exists ;-)

    "http://pycurl.sourceforge.net/tests/404_NOT_FOUND",

)

# Read list of URIs from file specified on commandline

try:

    urls = open(sys.argv[1], "rb").readlines()

except IndexError:

    # No file was specified

    pass

# init

m = pycurl.CurlMulti()

m.handles = []

for url in urls:

    c = pycurl.Curl()

    # save info in standard Python attributes

    c.url = url.strip()

    c.body = StringIO()

    c.http_code = -1

    m.handles.append(c)

    # pycurl API calls

    c.setopt(c.URL, c.url)

    c.setopt(c.WRITEFUNCTION, c.body.write)

    c.setopt(c.FOLLOWLOCATION,True)

    m.add_handle(c)

# get data

num_handles = len(m.handles)

while num_handles:

     while 1:

         ret, num_handles = m.perform()

         print ret,num_handles

         if ret != pycurl.E_CALL_MULTI_PERFORM:

             break

     # currently no more I/O is pending, could do something in the meantime

     # (display a progress bar, etc.)

     m.select(1.0)

# close handles

for c in m.handles:

    # save info in standard Python attributes

    c.http_code = c.getinfo(c.HTTP_CODE)

    # pycurl API calls

    m.remove_handle(c)

    c.close()

m.close()

# print result

for c in m.handles:

    data = c.body.getvalue()

    if 0:

        print "**********", c.url, "**********"

        print data

    else:

        print "%-53s http_code %3d, %6d bytes" % (c.url, c.http_code, len(data))

　　

 
 

例3

import os, sys

try:

    from cStringIO import StringIO

except ImportError:

    from StringIO import StringIO

import pycurl

urls = (

    "http://curl.haxx.se",

    "http://www.python.org",

    "http://pycurl.sourceforge.net",

    "http://pycurl.sourceforge.net/THIS_HANDLE_IS_CLOSED",

)

# init

m = pycurl.CurlMulti()

m.handles = []

for url in urls:

    c = pycurl.Curl()

    # save info in standard Python attributes

    c.url = url

    c.body = StringIO()

    c.http_code = -1

    c.debug = 0

    m.handles.append(c)

    # pycurl API calls

    c.setopt(c.URL, c.url)

    c.setopt(c.WRITEFUNCTION, c.body.write)

    c.setopt(c.FOLLOWLOCATION,True)

    m.add_handle(c)

# debug - close a handle

if 1:

    c = m.handles[3]

    c.debug = 1

    c.close()

# get data

num_handles = len(m.handles)

while num_handles:

    while 1:

        ret, num_handles = m.perform()

        if ret != pycurl.E_CALL_MULTI_PERFORM:

            break

    # currently no more I/O is pending, could do something in the meantime

    # (display a progress bar, etc.)

    m.select(1.0)

# close handles

for c in m.handles:

    # save info in standard Python attributes

    try:

        c.http_code = c.getinfo(c.HTTP_CODE)

    except pycurl.error:

        # handle already closed - see debug above

        assert c.debug

        c.http_code = -1

    # pycurl API calls

    if 0:

        m.remove_handle(c)

        c.close()

    elif 0:

        # in the C API this is the wrong calling order, but pycurl

        # handles this automatically

        c.close()

        m.remove_handle(c)

    else:

        # actually, remove_handle is called automatically on close

        c.close()

m.close()

# print result

for c in m.handles:

    data = c.body.getvalue()

    if 0:

        print "**********", c.url, "**********"

    else:

        print "%-53s http_code %3d, %6d bytes" % (c.url, c.http_code, len(data)）

　　

 
  

可以使用multi接口来缩短访问很多url的时间

假设一个文件中包含了很多个url，现在要通过脚本去访问每个url判断返回码是不是200

文件中共有87个url

方法一 使用python的for语句顺序访问每个url

import os,sys

import pycurl

from StringIO import StringIO

try:

   if sys.argv[1]=="-":

      urls=sys.stdin.readlines()

   else:

      urls=open(sys.argv[1],'rb').readlines()

   #print urls

except:

   print "Usage: %s check_urls.txt <file with urls to check>" %sys.argv[0]

   raise SystemExit

class Curl:

   def __init__(self,url):

       self.url=url

       self.body=StringIO()

       self.http_code=0

       self._curl=pycurl.Curl()

       self._curl.setopt(pycurl.URL,self.url)

       self._curl.setopt(pycurl.WRITEFUNCTION,self.body.write)

       self._curl.setopt(pycurl.FOLLOWLOCATION,True)

       self._curl.setopt(pycurl.NOSIGNAL,1)

   def perform(self):

       self._curl.perform()

   def close(self):

       self.http_code=self._curl.getinfo(pycurl.HTTP_CODE)

       self._curl.close()

for url in urls:

   url=url.strip()

   if not url or url[0] == '#':

     continue

   c=Curl(url)

   c.perform()

   c.close()

   print  url, c.http_code

　　

real    2m46.134s

user    0m0.134s

sys 0m0.185s

　　

 
 
 
 

方法二 使用pycurl的CurlMulti()函数

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from StringIO import StringIO
import pycurl
 
# We should ignore SIGPIPE when using pycurl.NOSIGNAL - see
# the libcurl tutorial for more info.
try:
   import signal
   from signal import SIGPIPE,SIG_ING
   signal.signal(signal.SIGPIPE,signal.SIG_IGN)
except ImportError:
   pass
 
 
# need a given txt file contains urls
try:
   if sys.argv[1]=="-":
      urls=sys.stdin.readlines()
   else:
      urls=open(sys.argv[1],'rb').readlines()
   #print urls
except:
   print "Usage: %s check_urls.txt <file with urls to check>" %sys.argv[0]
   raise SystemExit
 
class Curl:
   def __init__(self,url):
       self.url=url
       self.body=StringIO()
       self.http_code=0
 
       self._curl=pycurl.Curl()
       self._curl.setopt(pycurl.URL,self.url)
       self._curl.setopt(pycurl.FOLLOWLOCATION,True)
       self._curl.setopt(pycurl.WRITEFUNCTION,self.body.write)
       self._curl.setopt(pycurl.NOSIGNAL,1)
       self._curl.debug=0
 
   def perform(self):
       self._curl.perform()
 
   def close(self):
      try:
        self.http_code=self._curl.getinfo(pycurl.HTTP_CODE)
      except pycurl.error:
        assert c.debug
        self.http_code=0
      self._curl.close()
 
 
 
def print_result(items):
 
    for c in items:
        data=c.body.getvalue()
        if 0:
            print "***************",c.url,"******************"
            print data
        elif 1:
            print "%-60s        %3d     %6d" %(c.url,c.http_code,len(data))
 
 
 
def test_multi():
    handles=[]
    m=pycurl.CurlMulti()
    for url in urls:
        url=url.strip()
        if not url or url[0] == '#':
           continue
        c=Curl(url)
        m.add_handle(c._curl)
        handles.append(c)
 
    while 1:
        ret,num_handles=m.perform()
        if ret!= pycurl.E_CALL_MULTI_PERFORM:
           break
 
    while num_handles:
        m.select(5.0)
        while 1:
            ret,num_handles=m.perform()
            if ret!= pycurl.E_CALL_MULTI_PERFORM:
                break
    for c in handles:
        c.close()
    m.close()
 
 
    print_result(handles)
 
 
 
 
if 1:
  test_multi()
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real    2m46.049s
user    0m0.082s
sys 0m0.132s

在pycurl作者给的案例中，使用CurlMulti()接口处理多个url速度是最快的，但是当url数量多时速度并不快，而且有部分url还不能获取正确的返回值

方法三 使用python的多线程模块

python由于有GIL全局解释器锁的存在，python提供的threading模块不能充分利用多线程的优势，在多核CPU服务器上，统一时刻实际上只有一个线程在运行，其他线程都处于锁定状态。所以python的threading模块不适合用于处理CPU密集型任务，相反，threading线程数据量越多，速度越慢。但是对于I/O密集型或者网络密集型任务，还是可以使用threading模块

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import os,sys,time
import threading
import Queue
 
try:
   from cStringIO import StringIO
except ImportError:
   from StringIO import StringIO
import pycurl
 
# We should ignore SIGPIPE when using pycurl.NOSIGNAL - see
# the libcurl tutorial for more info.
try:
   import signal
   from signal import SIGPIPE,SIG_ING
   signal.signal(signal.SIGPIPE,signal.SIG_IGN)
except ImportError:
   pass
 
 
# need a given txt file contains urls
try: 
   if sys.argv[1]=="-":
      urls=sys.stdin.readlines()
   else:
      urls=open(sys.argv[1],'rb').readlines()
   #print urls
except:
   print "Usage: %s check_urls.txt <file with urls to check>" %sys.argv[0]
   raise SystemExit
  
class Curl:
   def __init__(self,url):
       self.url=url
       self.body=StringIO()
       self.http_code=0
        
       self._curl=pycurl.Curl()
       self._curl.setopt(pycurl.URL,self.url)
       self._curl.setopt(pycurl.FOLLOWLOCATION,True)
       self._curl.setopt(pycurl.CONNECTTIMEOUT,15)
       self._curl.setopt(pycurl.TIMEOUT,15)
       self._curl.setopt(pycurl.WRITEFUNCTION,self.body.write)
       self._curl.setopt(pycurl.NOSIGNAL,1)
       self._curl.debug=0
    
   def perform(self):
       self._curl.perform()
    
   def close(self):
      try:
        self.http_code=self._curl.getinfo(pycurl.HTTP_CODE)
      except pycurl.error:
        assert c.debug
        self.http_code=0 
      self._curl.close()
 
 
queue=Queue.Queue()
for url in urls:
    url=url.strip()
    if not url or url[0] == "#":
       continue
    queue.put(url)
     
assert queue.queue, "no urls are given"
num_urls=len(queue.queue)
#num_conn=min(num_conn,num_urls)
num_conn=num_urls
#assert 1 <= num_conn < = 1000,"invalid number of concurrent connections"
 
class WorkerThread(threading.Thread):
     def __init__(self,queue):
         threading.Thread.__init__(self)
         self.queue=queue
   
     def run(self):
         while 1:
             try:
                url=self.queue.get_nowait()
             except Queue.Empty:
                raise SystemExit
             c=Curl(url)
             c.perform()
             c.close()
             print "http_url:" + url + "\t" + "http_code:" + str(c.http_code)
#start a bunch of threads                
threads=[]
for dummy in range(num_conn):
    t=WorkerThread(queue)
    t.start()
    threads.append(t)
 
#wait for all threads to finish
for thread in threads:
    thread.join()
1
2
3
real    0m10.500s
user    0m0.149s
sys 0m0.196s

可以看到时间明显比以上两种方法所短了很多

所以，对于有大量url需要用pycurl来处理时，应该结合threading模块

参考资料：

http://pycurl.sourceforge.net/

http://pycurl.io/docs/latest/index.html

https://curl.haxx.se/libcurl/

https://curl.haxx.se/libcurl/c/libcurl-multi.html

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