python name mangling example with class

mangling_example.py

"""
Below value called `private` or `protected` is not accredited expression.
I choose those expression for easy to understand scope.
"""

class MyClass:
    __private_value = 'private'
    _protected_value = 'protected'
    public_value = 'public'

    def __init__(self, private='', protected='', public=''):
        if private:
            self.__private_value = private
        if protected:
            self._protected_value = protected
        if public:
            self.public_value = public

    def print_private(self):
        print(self.__private_value)

my_class =  MyClass()

print(my_class.public_value)
print(my_class._protected_value)
my_class.print_private()
print(my_class.__private_value)

Result

public
protected
private
Traceback (most recent call last):
  File "scope/private.py", line 22, in <module>
    print(my_class.__private_value)
AttributeError: 'MyClass' object has no attribute '__private_value'