Private/non-public data

	There is no technical way of preventing users from manipulating data and methods in an object
	Convention: attributes and methods starting with an underscore are treated as non-public (``protected'')
	Names starting with a double underscore are considered strictly private (Python mangles class name with method name in this case: obj.__some has actually the name _obj__some)

class MyClass:
    def __init__(self):
        self._a = False    # non-public
        self.b = 0         # public
        self.__c = 0       # private