Python私有变量（Private Variable）

Variables can be private which can be useful on many occasions. A private variable can only be changed within a class method and not outside of the class.

Objects can hold crucial data for your application and you do not want that data to be changeable from anywhere in the code.

class Car:

    __maxspeed = 0
    __name = ""

    def __init__(self):
        self.__maxspeed = 200
        self.__name = "Supercar"

    def drive(self):
        print 'driving. maxspeed ' + str(self.__maxspeed)

redcar = Car()
redcar.drive()
redcar.__maxspeed = 10  # will not change variable because its private
redcar.drive()

If you want to change the value of a private variable, a setter method is used. This is simply a method that sets the value of a private variable.