questions about multiprocessing

[Vincent Ren]

I've got some new problems and I tried to search on Google but got no
useful information.


I want to download some images with multiprocessing.pool
In my class named Renren, I defined two methods:

    def getPotrait(self, url):
        # get the current potraits of a friend on Renren.com
        try:
            r = urllib2.urlopen(url)
        except urllib2.URLError:
            print "Time out"

        tmp = re.search('large_[\d\D]*.jpg', url)
        image_name = tmp.group()

        img = r.read()
        output = open(image_name, 'wb')
        output.write(img)
        output.close()

    def getLargePotraits(self):

        tasks = self.makeTaskList()
        pool = Pool(processes = 3)
        pool.map(self.getPotrait, tasks)


tasks is a list of URLs of images, I want to download these images and
save them locally.

In another python file, I wrote this:

   from renren import Renren

   # get username and password for RenRen.com
   username = raw_input('Email: ')
   password = raw_input('Password: ')
   print


   a = Renren(username, password)
   a.login()
   a.getLargePotraits()



However, when I try to run this file, I received an error message:

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.6/threading.py", line 532, in
__bootstrap_inner
    self.run()
  File "/usr/lib/python2.6/threading.py", line 484, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.6/multiprocessing/pool.py", line 225, in
_handle_tasks
    put(task)
PicklingError: Can't pickle <type 'instancemethod'>: attribute lookup
__builtin__.instancemethod failed