NameError在运行程序时发生，如何修复？

Question

基本上，我的代码创建了不同的分形并将它们显示在画布上。但是，当我去运行程序时，会弹出以下错误消息：(类SierpinskiTriangle(分形)：NameError: name 'Fractal‘未定义)。我知道这个特定的错误发生在变量未定义或定义不正确时，但我找不到问题所在。有什么帮助吗？

from tkinter import *
from math import sqrt, sin, cos, pi as PI
from random import randint

# the 2D point class    
class Point(object):
    def __init__(self, x=0.0, y=0.0):
        self.x = float(x)
        self.y = float(y)

# Accessors and mutators
    @property
    def x(self):
        return self._x
    @x.setter
    def x(self, value):
        self._x = value

    @property
    def y(self):
        return self._y

    @y.setter
    def y(self, value):
        self._y = value

# Functions used to calculate the distance and the midpoint
    def dist(self, a):
        return sqrt ((self.x-a.x)**2+(self.y-a.y)**2)

    def midpt(self, a):
        return Point((self.x+a.x)/2, (self.y+a.y)/2)
    
# The magic function
    def magic(self, a, triangle):
        trianglex = triangle
        if (self.x > a.x):
            trianglex = 1.0 - triangle
        triangley = triangle
        if (self.y > a.y):
            triangley = 1.0 - triangle
        x = abs(self.x - a.x) * trianglex + min(self.x, a.x)
        y = abs(self.y - a.y) * triangley + min(self.y, a.y)
        return Point(x,y)

# Function used to define the string
    def __str__(self):
        return "({}, {})".format(self.x, self.y)
    
# the coordinate system class: (0,0) is in the top-left corner
# inherits from the Canvas class of Tkinter
class ChaosGame(Canvas):
    def __init__(self, master):
        Canvas.__init__(self, master, bg="white")
        self.pack(fill=BOTH, expand=1)
        
# sets the dimensions and the radius, as well as the color
        self.dimensions = {"MIN_X":2, "MAX_X":WIDTH-9, "MIN_Y":2, "MAX_Y":HEIGHT-9}
        self.dimensions["MID_Y"] = (self.dimensions["MIN_Y"]+self.dimensions["MAX_Y"])/2
        self.dimensions["MID_X"] = (self.dimensions["MIN_X"]+self.dimensions["MAX_X"])/2
        self.vertexRadius = 1
        self.vertexColor = "blue"
        self.pointRadius = 0
        self.pointColor = "black"
    

# Function used to plot the generated points for the SierpinskiTriangle
    def plot_Values(self, points):
        if(points == "SierpinskiTriangle"):
            p1 = SierpinskiTriangle(self.dimensions)
            for vertex in p1.vertices:
                self.plot_point(vertex, self.vertexColor, self.vertexRadius)
            p = p1.vertices[randint(0, len(p1.vertices)-1)]
            for i in range(p1.num_points):
                p = p.magic(p1.vertices[randint(0, len(p1.vertices)-1)], p1.triangle)
                self.plot_point(p, self.pointColor, self.pointRadius)
                        

# Creates the rest of the fractal classes
        if(points == "Pentagon"):
            p1 = Pentagon(self.dimensions)
            for vertex in p1.vertices:
                self.plot_point(vertex, self.vertexColor, self.vertexRadius)
            p = p1.vertices[randint(0, len(p1.vertices)-1)]
            for i in range(p1.num_points):
                p = p.interpt(p1.vertices[randint(0, len(p1.vertices)-1)], p1.triangle)
                self.plot_point(p, self.pointColor, self.pointRadius)

        if(points == "Hexagon"):
            p1 = Hexagon(self.dimensions)
            for vertex in p1.vertices:
                self.plot_point(vertex, self.vertexColor, self.vertexRadius)
            p = p1.vertices[randint(0, len(p1.vertices)-1)]
            for i in range(p1.num_points):
                p = p.interpt(p1.vertices[randint(0, len(p1.vertices)-1)], p1.triangle)
                self.plot_point(p, self.pointColor, self.pointRadius)                        
                        
        if(points == "Octagon"):
            p1 = Octagon(self.dimensions)
            for vertex in p1.vertices:
                self.plot_point(vertex, self.vertexColor, self.vertexRadius)
            p = p1.vertices[randint(0, len(p1.vertices)-1)]
            for i in range(p1.num_points):
                p = p.interpt(p1.vertices[randint(0, len(p1.vertices)-1)], p1.triangle)
                self.plot_point(p, self.pointColor, self.pointRadius)

        if(points == "SierpinskiCarpet"):
            p1 = SierpinskiCarpet(self.dimensions)
            for vertex in p1.vertices:
                self.plot_point(vertex, self.vertexColor, self.vertexRadius)
            p = p1.vertices[randint(0, len(p1.vertices)-1)]
            for i in range(p1.num_points):
                p = p.interpt(p1.vertices[randint(0, len(p1.vertices)-1)], p1.triangle)
                self.plot_point(p, self.pointColor, self.pointRadius)


# Function used to set the color of the points and used to find the radius
    def plot_point(self, point, color, radius):
        self.create_oval(point.x , point.y , point.x + 2*radius, point.y + 2*radius, outline= color , fill= color)

# Code for the fractals
class SierpinskiTriangle(Fractal):
    def __init__(self, canvas):
        Fractal.__init__(self, canvas)
        v1 = Point(self.dimensions["MID_X"], self.dimensions["MIN_Y"])
        v2 = Point(self.dimensions["MIN_X"], self.dimensions["MAX_Y"])
        v3 = Point(self.dimensions["MAX_X"], self.dimensions["MAX_Y"])
        self.vertices = [ v1, v2, v3 ]

class SierpinskiCarpet(Fractal):
    def __init__(self, canvas):
        Fractal.__init__(self, canvas)
        v1 = Point(self.dimensions["MIN_X"], self.dimensions["MIN_Y"])
        v2 = Point(self.dimensions["MID_X"], self.dimensions["MIN_Y"])
        v3 = Point(self.dimensions["MIN_X"], self.dimensions["MIN_Y"])
        v4 = Point(self.dimensions["MIN_X"], self.dimensions["MID_Y"])
        v5 = Point(self.dimensions["MIN_X"], self.dimensions["MID_Y"])
        v6 = Point(self.dimensions["MIN_X"], self.dimensions["MAX_Y"])
        v7 = Point(self.dimensions["MID_X"], self.dimensions["MAX_Y"])
        v8 = Point(self.dimensions["MIN_X"], self.dimensions["MAX_Y"])
        self.vertices = [ v1, v2, v3, v4, v5, v6, v7, v8 ]
        self.num_points = 100000
        self.traingle = 0.66

class Pentagon(Fractal):
    def __init__(self, canvas):
        Fractal.__init__(self, canvas)
        v1 = Point(self.dimensions["MID_X"] + self.dimensions["MID_X"] * cos(2 * PI / 5 + 60), (self.frac_y(0.5375) + self.dimensions["MID_Y"] * sin(2 * PI / 5 + 60)))
        v2 = Point(self.dimensions["MID_X"] + self.dimensions["MID_X"] * cos(4 * PI / 5 + 60), (self.frac_y(0.5375) + self.dimensions["MID_Y"] * sin(4 * PI / 5 + 60)))
        v3 = Point(self.dimensions["MID_X"] + self.dimensions["MID_X"] * cos(6 * PI / 5 + 60), (self.frac_y(0.5375) + self.dimensions["MID_Y"] * sin(6 * PI / 5 + 60)))
        v4 = Point(self.dimensions["MID_X"] + self.dimensions["MID_X"] * cos(8 * PI / 5 + 60), (self.frac_y(0.5375) + self.dimensions["MID_Y"] * sin(8 * PI / 5 + 60)))
        v5 = Point(self.dimensions["MID_X"] + self.dimensions["MID_X"] * cos(10 * PI / 5 + 60), (self.frac_y(0.5375) + self.dimensions["MID_Y"] * sin(10 * PI / 5 + 60)))
        self.vertices = [ v1, v2, v3, v4, v5 ]
        self.triangle = 0.618

class Hexagon(Fractal):
    def __init__(self, canvas):
        Fractal.__init__(self, canvas)
        v1 = Point(self.dimensions["MID_X"], self.dimensions["MIN_Y"])
        v2 = Point(self.dimensions["MIN_X"], self.frac_y(0.25))
        v3 = Point(self.dimensions["MAX_X"], self.frac_y(0.25))
        v4 = Point(self.dimensions["MIN_X"], self.frac_y(0.75))
        v5 = Point(self.dimensions["MAX_X"], self.frac_y(0.75))
        v6 = Point(self.dimensions["MID_X"], self.dimensions["MAX_Y"])
        self.vertices = [ v1, v2, v3, v4, v5, v6 ]
        self.triangle = 0.665
        
class Octagon(Fractal):
    def __init__(self, canvas):
        Fractal.__init__(self, canvas)
        v1 = Point(self.frac_x(0.2925), self.dimensions["MIN_Y"])
        v2 = Point(self.frac_x(0.7075), self.dimensions["MIN_Y"])
        v3 = Point(self.dimensions["MIN_X"], self.frac_y(0.2925))
        v4 = Point(self.dimensions["MAX_X"], self.frac_y(0.2925))
        v5 = Point(self.dimensions["MIN_X"], self.frac_y(0.7075))
        v6 = Point(self.dimensions["MAX_X"], self.frac_y(0.7075))
        v7 = Point(self.frac_x(0.2925), self.dimensions["MAX_Y"])
        v8 = Point(self.frac_x(0.7075), self.dimensions["MAX_Y"])
        self.vertices = [ v1, v2, v3, v4, v5, v6, v7, v8 ]
        self.num_points = 75000
        self.triangle = 0.705
        
##############################
######## MAIN CODE############      
# sets the size of the canvas 
WIDTH = 700
HEIGHT = 550
# the implemented fractals
Fractals = ["SierpinskiTriangle", "SierpinskiCarpet", "Pentagon", "Hexagon", "Octagon"]

# create the fractals in individual (sequential) windows
for i in Fractals:  
    window = Tk()
    window.geometry("{}x{}".format(WIDTH, HEIGHT))
    window.title("The Chaos Game")
# create the chaos game as a Tkinter canvas inside the window
    s = ChaosGame(window)
# plot some random points
    s.plot_Values(i)
# wait for the window to close
    window.mainloop()

Answer 1

关于您的代码：

class SierpinskiTriangle(Fractal):

这是试图将SierpinskiTriangle类定义为来自Fractal的派生类。

您不会在代码中的任何一点定义(或导入) Fractal，这就是您获得错误的原因。

因此，解决方案是在尝试对Fractal类进行子类分类之前定义或导入它。