利用poster模块发一个post文件请求，怎么获取发出请求的头信息？（高分）

利用poster模块发一个post文件请求，如何获取发出请求的头信息？（高分）
求教一个问题，我用以下代码发出的请求，我如何才能获取到我发出请求的头部信息呢？谢谢！
我用的第三方模块poster来发的请求。

Python code

import urllib2
import poster

opener = poster.streaminghttp.register_openers()
url='http://api.qcloud.cn/intf.php?method=Qds.put&v=1&key=desktop-weiboauth-87000945&lsig=e3f9e50869aa31251870e542dda4c90a&cs=2b2029835e1a53f2e0f233e14973cfb4'
params = {'file': open(r"e:\1.txt","rb")}
datagen, headers = poster.encode.multipart_encode(params) 
request = urllib2.Request(url,datagen, headers)
result = urllib2.urlopen(request)
print result.read(),result.info()

我在网上找的方法，但是会报错，

Python code

import urllib2
import poster

opener = poster.streaminghttp.register_openers()
url='http://api.qcloud.cn/intf.php?method=Qds.put&v=1&key=desktop-weiboauth-87000945&lsig=e3f9e50869aa31251870e542dda4c90a&cs=2b2029835e1a53f2e0f233e14973cfb4'
httpHandler = urllib2.HTTPHandler(debuglevel=1)
#httpsHandler = urllib2.HTTPSHandler(debuglevel=1)
opener = urllib2.build_opener(httpHandler)
urllib2.install_opener(opener)
params = {'file': open(r"e:\1.txt","rb")}
datagen, headers = poster.encode.multipart_encode(params) 
request = urllib2.Request(url,datagen, headers)
result = urllib2.urlopen(request)
print result.read(),result.info()

错误信息：
send: 'POST http://api.qcloud.cn/intf.php?method=Qds.put&v=1&key=desktop-weiboauth-87000945&lsig=e3f9e50869aa31251870e542dda4c90a&cs=2b2029835e1a53f2e0f233e14973cfb4 HTTP/1.1\r\nAccept-Encoding: identity\r\nContent-Length: 181\r\nHost: api.qcloud.cn\r\nContent-Type: multipart/form-data; boundary=b673099801d548aa9e4cef450e9530df\r\nConnection: close\r\nUser-Agent: Python-urllib/2.7\r\n\r\n'
Traceback (most recent call last):
  File "E:\workspace\fgos\TestGood\post_test.py", line 38, in <module>
send: <poster.encode.multipart_yielder instance at 0x011FE288>
  result = urllib2.urlopen(request)
  File "C:\Python27\lib\urllib2.py", line 126, in urlopen
  return _opener.open(url, data, timeout)
  File "C:\Python27\lib\urllib2.py", line 394, in open
  response = self._open(req, data)
  File "C:\Python27\lib\urllib2.py", line 412, in _open
  '_open', req)
  File "C:\Python27\lib\urllib2.py", line 372, in _call_chain
  result = func(*args)
  File "C:\Python27\lib\urllib2.py", line 1199, in http_open
  return self.do_open(httplib.HTTPConnection, req)
  File "C:\Python27\lib\urllib2.py", line 1168, in do_open
  h.request(req.get_method(), req.get_selector(), req.data, headers)
  File "C:\Python27\lib\httplib.py", line 955, in request
  self._send_request(method, url, body, headers)
  File "C:\Python27\lib\httplib.py", line 989, in _send_request
  self.endheaders(body)
  File "C:\Python27\lib\httplib.py", line 951, in endheaders
  self._send_output(message_body)
  File "C:\Python27\lib\httplib.py", line 815, in _send_output
  self.send(message_body)
  File "C:\Python27\lib\httplib.py", line 787, in send
  self.sock.sendall(data)
  File "C:\Python27\lib\socket.py", line 224, in meth
  return getattr(self._sock,name)(*args)
TypeError: must be string or buffer, not instance

如果我去掉“request = urllib2.Request(url,datagen, headers)”这句的datagen和header参数，就可以获取到头信息。
但是我需要获取的确是发出一个post文件请求的头信息，这怎么搞定啊，是poster模块的问题吗？如何更好的解决呢？

------解决方案--------------------