python之实例没有属性_pi

我正在尝试制作这样的 Python 模块:

class square: 
    def _init_(self): 
        self._length = 0 
        self._perimeter = 0 
        self._area = 0 
    def setLength(self, length): 
        self._length = float(length) 
        self._perimeter = 0 
        self._area = 0 
    def getLength(self): 
        return self._length 
    def getPerimeter(self): 
        if self._perimeter == 0: 
            self._perimeter = float(self._length * 4) 
        return self._perimeter 
    def getArea(self): 
        if self._area == 0: 
            self._area = float(self._length * self._length) 
        return self._area 
class rectangle: 
    def _init_(self): 
        self._length = 0 
        self._width = 0 
        self._perimeter = 0 
        self._area = 0 
    def setLength(self, length): 
        self._length = float(length) 
        self._perimeter = 0 
        self._area = 0 
    def getLength(self): 
        return self._length 
    def setWidth(self, width): 
        self._width = float(width) 
        self._perimeter = 0 
        self._area = 0 
    def getWidth(self): 
        return self._width 
    def getPerimeter(self): 
        if self._perimeter == 0: 
            perim1 = float(self._length * 2) 
            perim2 = float(self._width * 2) 
            self._perimeter = float(perim1 + perim2) 
        return self._perimeter 
    def getArea(self): 
        if self._area == 0: 
            self._area = float(self._length * self._width) 
        return self._area 
class circle: 
    def _init_(self): 
        self._radius = 0 
        self._diameter = 0 
        self._circumference = 0 
        self._pi = 3.14159265 
    def setRadius(self, radius): 
        self._radius = float(radius) 
        self._diameter = float(self._radius * 2) 
        self._circumference = 0 
    def setDiameter(self, diameter): 
        self._diameter = float(diameter) 
        self._radius = float(self._diameter / 2) 
        self._circumference = 0 
    def getRadius(self): 
        return self._radius 
    def getDiameter(self): 
        return self._diameter 
    def getPi(self): 
        return self._pi 
    def getCircumference(self): 
        if self._circumference == 0: 
            self._circumference = float(self._diameter * self._pi) 
        return self._circumference 
class triangle: 
    def _init_(self): 
        self._side = [] 
        self._side[0] = 0 
        self._side[1] = 0 
        self._side[2] = 0 
        self._side[3] = 0 
        self._angle = [] 
        self._angle[0] = 0 
        self._angle[1] = 0 
        self._angle[2] = 0 
        self._angle[3] = 0 
        self._perimeter = 0 
        self._area = 0 
    def setSide(self, side, length): 
        self._side[side] = float(length) 
    def getSide(self, side): 
        return self._side[side] 
    def getPerimeter(self): 
        if self._perimeter == 0: 
            self._perimeter = side[1] + side[2] + side[3] 
        return self._perimeter 
    def setAngle(self, angle, measure): 
        self._angle[angle] = float(measure) 
    def getAngle(self, angle): 
        if self._angle[angle] == 0: 
            if angle == 1: 
                angle1 = self._angle[2] 
                angle2 = self._angle[3] 
            elif angle == 2: 
                angle1 = self._angle[1] 
                angle2 = self._angle[3] 
            elif angle == 3: 
                angle1 = self._angle[1] 
                angle2 = self._angle[2] 
            anglet = angle1 + angle2 
            angler = float(180) - anglet 
            self._angle[angle] = angler 
        return self.angle[angle] 

它是名为 Mathworks 的包的一部分。调用代码是这样的:

import mathworks as mw 
mycircle = mw.shapes.circle() 
mycircle.setDiameter(5) 
circum = mycircle.getCircumference() 
print circim 

当我尝试两次运行第二个模块时，我得到了这个:

Traceback (most recent call last): 
  File "<string>", line 254, in run_nodebug 
  File "<module1>", line 21, in <module> 
  File "<module1>", line 17, in main 
  File "C:\Python27\lib\site-packages\mathworks\shapes.py", line 70, in getCircumference 
    self._circumference = float(self._diameter * self._pi) 
AttributeError: circle instance has no attribute '_pi' 

怎么了？如果我将 self._pi 替换为 3.14159265，它会起作用，但我需要它以其他方式起作用。

请您参考如下方法:

你没有正确命名你的初始值设定项，它的两端都需要双下划线:

def __init__(self): 

您需要为您的所有类(class)更正。

因为您没有正确命名它们，所以当您创建类的实例时它们不会运行。

您将遇到的下一个问题是您的 triangle 初始化程序；您不能在空列表中寻址索引。改为一次性创建整个列表:

def __init__(self): 
    self._side = [0, 0, 0, 0] 
    self._angle = [0, 0, 0, 0] 
    self._perimeter = 0 
    self._area = 0