list of user's variables in the interpreter

[Gribouillis]

If you want to access the parameter names of a function or the local variables defined in this function, the correct way is to use module inspect and attributes of code objects, for example:

>>> import inspect
>>> def spam(a, b, c='foo'):
...     bar = a + c
...     qux = [x for x in b if x.is_baz()]
... 
>>> spam.__code__.co_varnames
('a', 'b', 'c', 'bar', 'qux')
>>> s = inspect.signature(spam)
>>> s.parameters
mappingproxy(OrderedDict([('a', <Parameter "a">), ('b', <Parameter "b">), ('c', <Parameter "c='foo'">)]))