python中的构造函数和类

Question

我是python的新手，我正在努力学习类的概念。我想问一些问题：

1. 是否必须编写__init__(self)构造函数？
2. 如何运行包含类的脚本？
3. 在此示例中，它为self引发了错误？

代码：

 #An example of a class
    class Shape:
        def __init__(self,x,y):
            self.x = x
            self.y = y
        description = "This shape has not been described yet"
        author = "Nobody has claimed to make this shape yet"
        def area(self):
            return self.x * self.y
        def perimeter(self):
            return 2 * self.x + 2 * self.y
        def describe(self,text):
            self.description = text
        def authorName(self,text):
            self.author = text
        def scaleSize(self,scale):
            self.x = self.x * scale
        self.y = self.y * scale

错误：

Traceback (most recent call last):
  File "C:/Python27/cls.py", line 2, in <module>
    class Shape:
  File "C:/Python27/cls.py", line 18, in Shape
    self.y = self.y * scale
NameError: name 'self' is not defined

Answer 1

1）不，这不是强制性的。构造函数通常用于初始化。如果您实现了构造函数，则取决于您要执行的操作。

3）这似乎是一个缩进问题：

class Shape:
    def __init__(self,x,y):
        self.x = x
        self.y = y
        self.description = "This shape has not been described yet"
        self.author = "Nobody has claimed to make this shape yet"
    def area(self):
        return self.x * self.y
    def perimeter(self):
        return 2 * self.x + 2 * self.y
    def describe(self,text):
        self.description = text
    def authorName(self,text):
        self.author = text
    def scaleSize(self,scale):
        self.x = self.x * scale
        self.y = self.y * scale