属性错误：对象没有属性 Python

Attribute error: Object has no attribute Python

提问by Chubzorz

I am trying to program a version of conway's game of life however I keep getting the message 'Cell' Object Has no attribute 'nextState'when it seems like it should declare the value of nextState before asking to reference it. here is my code:

我正在尝试编写一个版本的康威生活游戏，但是'Cell' Object Has no attribute 'nextState'当它似乎应该在要求引用它之前声明 nextState 的值时，我不断收到消息。这是我的代码：

from tkinter import *
root = Tk()

class Cell (Button):
    Dead = 0
    Live = 1

    def __init__ (self,parent):
        Button.__init__(self,parent, relief = "raised" , width = 2 , borderwidth = 1 , command = self.onpress)
        self.displayState(Cell.Dead)

    def onpress (self):
        if self.state == Cell.Live:
            self.displayState(Cell.Dead)
        elif self.state == Cell.Dead:
            self.displayState(Cell.Live)

    def setNextState (self , Neighbours):
        if self.state == Cell.Live and (Neighbours < 2 or Neighbours > 3):
            self.nextState = Cell.Dead
        elif self.state == Cell.Dead and Neighbours == 3:
            self.nextState = Cell.Live
        elif self.state == Cell.Dead and Neighbours != 3:
            self.nextState = self.state

    def stepToNextState(self):
        self.displayState(self.nextState)

    def displayState (self , newstate):
        self.state = newstate
        if self.state == Cell.Live:
            self["bg"] = "black"
        if self.state == Cell.Dead:
            self["bg"] = "white"

class Grid:
    def __init__(self,parent,sizex,sizey):
        self.sizex = sizex
        self.sizey = sizey
        self.cells = []
        for a in range (0,self.sizex):
            rowcells = []
            for b in range (0, self.sizey):
                c = Cell(parent)
                c.grid(row=b , column=a)
                rowcells.append(c)
            self.cells.append(rowcells)

    def step (self):
        cells = self.cells
        for x in range (0,self.sizex):
            if x==0: x_down = self.sizex-1
            else: x_down = x-1
            if x==self.sizex-1: x_up = 0
            else: x_up = x+1
            for y in range(0,self.sizey):
                if y==0: y_down = self.sizey-1
                else: Y_down = y-1
                if y==self.sizey-1: y_up = 0
                else: y_up = y+1
                sum = cells[x_down][y].state + cells[x_up][y].state + cells[x][y_down].state + cells[x][y_up].state + cells[x_down][y_down].state +cells[x_up][y_up].state + cells[x_down][y_up].state + cells[x_up][y_down].state
                cells[x][y].setNextState(sum)
            for row in cells:
                for cell in row:
                    cell.stepToNextState()

    def clear(self):
        for row in self.cells:
            for cell in row:
                cell.displayState(Cell.Dead)

if __name__ == "__main__":
    frame = Frame(root)
    frame.pack()
    grid = Grid(frame,25,25)
    bottomFrame = Frame(root)
    bottomFrame.pack (side = BOTTOM)
    buttonStep = Button(bottomFrame , text="Step" , command=grid.step)
    buttonStep.pack(side = LEFT)
    buttonClear = Button(bottomFrame, text = "Clear", command=grid.clear)
    buttonClear.pack(side=LEFT , after=buttonStep)
    root.mainloop()

The error message is:

错误信息是：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python33\lib\tkinter\__init__.py", line 1442, in __call__
    return self.func(*args)
  File "C:\Users\Owner\Desktop\Other\Programs & Misc\Python\Tyler's Game of Life.py", line 65, in step
    cell.stepToNextState()
  File "C:\Users\Owner\Desktop\Other\Programs & Misc\Python\Tyler's Game of Life.py", line 27, in stepToNextState
    self.displayState(self.nextState)
AttributeError: 'Cell' object has no attribute 'nextState'

If anyone could point out where the error is occuring / what is causing it and possibly a way to fix it I would be very grateful.

如果有人能指出错误发生的位置/导致错误的原因以及可能的解决方法，我将不胜感激。

采纳答案by Blckknght

The issue appears to be that your for row in cellsloop is inside of your previous for x in range(0, self.sizex)loop. Here's what the stepmethod should look like if you get it correctly indented:

问题似乎是您的for row in cells循环在上一个for x in range(0, self.sizex)循环内。step如果正确缩进，方法应该如下所示：

def step (self):
    cells = self.cells
    for x in range (0,self.sizex):
        if x==0: x_down = self.sizex-1
        else: x_down = x-1
        if x==self.sizex-1: x_up = 0
        else: x_up = x+1
        for y in range(0,self.sizey):
            if y==0: y_down = self.sizey-1
            else: Y_down = y-1
            if y==self.sizey-1: y_up = 0
            else: y_up = y+1
            sum = cells[x_down][y].state + cells[x_up][y].state + cells[x][y_down].state + cells[x][y_up].state + cells[x_down][y_down].state +cells[x_up][y_up].state + cells[x_down][y_up].state + cells[x_up][y_down].state
            cells[x][y].setNextState(sum)
    for row in cells:                     # unindent these
        for cell in row:                  # lines by one
            cell.stepToNextState()        # level each

If all the indentation issues are taken care of (or were not in the original code), there's still an issue that maycause an issue in certain situations. The issue is that the Cell.setNextStatemethod doesn't handle every situation. Specifically, it doesn't set nextStateif a cell is alive and should stay so (it has two or three living neighbors). The lack of an elseon your chain of ifand elifstatements should have raised this as a red flag for me, but I overlooked it the first time I examined the function.

如果所有缩进问题都得到处理（或不在原始代码中），那么在某些情况下仍然存在可能导致问题的问题。问题是该Cell.setNextState方法不能处理所有情况。具体来说，它不会设置nextState一个单元格是否活着并且应该保持这样（它有两个或三个活着的邻居）。else你的ifandelif语句链上缺少 an对我来说应该是一个危险信号，但我第一次检查该函数时忽略了它。

Here's how it can be fixed:

以下是修复方法：

def setNextState (self , Neighbours):
    if self.state == Cell.Live and (Neighbours < 2 or Neighbours > 3):
        self.nextState = Cell.Dead
    elif self.state == Cell.Dead and Neighbours == 3:
        self.nextState = Cell.Live
    else: # remove the conditions on this block, all the state changes were handled above
        self.nextState = self.state