转python版本的curl工具pycurl学习

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()

1 2 3

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 + " " + "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()

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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