The functions defined in class need to provide a positional parameter of self, because when the class is instantiated, the instance object will be passed in and then bound to the function, so the code should be adjusted to:

# -*- coding:gb2312 -*-
class car:
    # 属性

    # 方法
    def __str__(self):
        return ("哈哈哈哈哈哈啊哈")

    def move(self):
        print("车在移动。")

    def Whistle(self):
        print("车载鸣笛。")


BMW = car()

print(BMW)

For the relationship between method and function, you can refer to my article: Python: The difference between functions and methods