1st person camera, "free view" style

Ouch - I didn’t catch that. This will work, on the other hand:

>>> class Dummy(object):
...     def __init__(self):
...             self.var = 5
... 
>>> d = Dummy()
>>> def my_func(cls):
...     cls.var = 4
... 
>>> my_func(d)
>>> d.var
4

Modifying a class inside a function it was passed to is almost never a good idea; that’s just asking for lots of hard-to-find, hidden bugs.