小编Wil*_*son的帖子

为什么这不起作用.这直接来自教科书.我收到一个属性错误,说self._area不存在.

from Tkinter import *
import math

class CircleArea(Frame):

    def __init__(self):
        """Sets up a window and widgets."""
        Frame.__init__(self)
        self.master.title("Circle Area")
        self.grid()

        #Label and field for radius
        self._radiusLabel = Label(self, text = "Radius")
        self._radiusLabel.grid(row = 0, column = 0)
        self._radiusVar = DoubleVar()
        self._radiusEntry = Entry(self, textvariable = self._radiusVar)
        self._radiusEntry.grid(row = 0, column = 1)

        #Label and field for the area
        self._areaLabel = Label(self, text = "Area")
        self._areaLabel.grid(row = 1, column = 0)
        self._areaVar = DoubleVar()
        self._areaEntry = Entry(self, textvariable = self._areaVar) …