We should probably have a single convention for attribute and module-level variable annotations that would at least be recommended (even if other ways would also work).

Here are some potential approaches:

• x = 0, x = '', etc. (at least for built-in types)
• x = Undefined(int)
• x = Undefined # type: int
• # var x: int (a proposal for PEP 484, still under discussion)
• x = ClassName()