How to modify private data using setter method?

class MyClass:
    def __init__(self):
        self.__data = 5
        
    def get_data(self):
        return self.__data
    
    def set_data(self, x): # Setter method
        self.__data = x
        
obj = MyClass()
obj.__data = 10
print(obj.get_data()) # return old value
obj.set_data(10) # Now, data modified using setter method
obj.get_data() # return new vlaue