The following types can be pickled (taken from python's pickle documentation):

• None, True, and False
• integers, floating point numbers, complex numbers
• strings, bytes, bytearrays
• tuples, lists, sets, and dictionaries containing only picklable objects
• functions defined at the top level of a module (using def, not lambda)
• built-in functions defined at the top level of a module
• classes that are defined at the top level of a module
• instances of such classes whose dict or the result of calling getstate() is picklable (see section Pickling Class Instances for details).

In contrast, safepickle currently does not save:

• complex numbers
• functions defined at the top level of a module (using def, not lambda)
• built-in functions defined at the top level of a module
• classes that are defined at the top level of a module
• instances of such classes whose the result of calling getstate() is picklable