Persist a class (not an instance)

[Kent Johnson]

Is there a way to persist a class definition (not a class instance, the actual 
class) so it can be restored later? A naive approach using pickle doesn't work:

 >>> import pickle
 >>> class Foo(object):
 ...   def show(self):
 ...     print "I'm a Foo"
 ...
 >>> p = pickle.dumps(Foo)
 >>> p
'c__main__\nFoo\np0\n.'

Hmm, doesn't look too promising. In a new interpreter:

 >>> import pickle
 >>> p='c__main__\nFoo\np0\n.'
 >>> Foo = pickle.loads(p)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "C:\Python24\lib\pickle.py", line 1394, in loads
    return Unpickler(file).load()
  File "C:\Python24\lib\pickle.py", line 872, in load
    dispatch[key](self)
  File "C:\Python24\lib\pickle.py", line 1104, in load_global
    klass = self.find_class(module, name)
  File "C:\Python24\lib\pickle.py", line 1140, in find_class
    klass = getattr(mod, name)
AttributeError: 'module' object has no attribute 'Foo'

The idea is to persist classes that are created and modified at runtime.

Thanks,
Kent
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