Find out why this script doesn't work (memcached test)

memcached_test.py

# -*- coding: utf-8 -*-
"""
Why memcached doesn't work?

We observe weird behaviour of the function save_object_to_cache(...)

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$ python /tmp/memcached_test.py

A new object <__main__.Wrapper object at 0x925f60c> with value "bar" has been created


Traceback (most recent call last):
  File "/tmp/memcached_test.py", line 34, in <module>
    save_object_to_cache('bar')
  File "/tmp/memcached_test.py", line 31, in save_object_to_cache
    client.set('foo', obj, 60)
  File "/usr/lib/python2.7/dist-packages/memcache.py", line 565, in set
    return self._set("set", key, val, time, min_compress_len)
  File "/usr/lib/python2.7/dist-packages/memcache.py", line 802, in _set
    return _unsafe_set()
  File "/usr/lib/python2.7/dist-packages/memcache.py", line 780, in _unsafe_set
    store_info = self._val_to_store_info(val, min_compress_len)
  File "/usr/lib/python2.7/dist-packages/memcache.py", line 751, in _val_to_store_info
    pickler.dump(val)
cPickle.PicklingError: Can't pickle <class '__main__.Wrapper'>: attribute lookup __main__.Wrapper failed

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"""
from memcache import Client

def save_object_to_cache(value):
    """
    Handy function to store a wrapped value in memcached
    """
    # connect to memcached
    client = Client(['127.0.0.1:11211'])

    # create a wrapper class to work with a value and initalize its instance
    class Wrapper(object):
        def __init__(self, value):
            self.value = value
        def get_value(self):
            return self.value
    obj = Wrapper(value)
    print '\nA new object %r with value "%s" has been created\n\n' % (obj, obj.get_value())

    # save the object to memcached
    client.set('foo', obj, 60)

if __name__ == '__main__':
    save_object_to_cache('bar')