在python GUI中更改按鈕顏色

Question

import sys
from tkinter import *

def run_GUI():
    # create the window
    root = Tk()
    frame = Frame(root)
    frame.pack()

    #modify root window
    root.title("Simple GUI")
    root.geometry("700x300") # w x h        
    def SP2T():     # Edit occurs here where I forgot to pit that the button was created in a called funtction
        #Creates Row
        frameSP2T = Frame(root)
        frameSP2T.pack(side = TOP)

        #Creating Buttons First Row
        button1 = Button(frameSP2T, padx=13, pady = 6, bd=4, text="SW02",fg = "black", command = SW02)
        button1.pack(side = LEFT)

    def SW02():
        print("SW02 is on")
        button1["fg"] = "green"

    #Sets up initial boot screen
    #Creates Row
    topframe = Frame(root)
    topframe.pack(side = TOP)

    #Creating Buttons First Row
    buttonA = Button(topframe, padx=13, pady = 6, bd=4, text="SP2T",fg = "black", command = SP2T)
    buttonA.pack(side = LEFT)

    buttonB = Button(topframe, padx=12, pady = 6, bd=4, text="SP4T",fg = "black")
    buttonB.pack(side = LEFT)

    buttonC = Button(topframe, padx=12, pady = 6, bd=4, text="SP12T",fg = "black")
    buttonC.pack(side = LEFT)

    buttonD = Button(topframe, padx=12, pady = 6, bd=4, text="QUIT", fg="red",command=frame.quit)
    buttonD.pack(side = LEFT)

    #Kick off event loop
    root.mainloop()
    return

run_GUI()

我得到了錯誤：

Traceback (most recent call last):

  File "C:\Python34\lib\tkinter\__init__.py", line 1487, in __call__

   return self.func(*args)

   File "C:\Python34\gui_attempt.py", line 25, in SW02

   button1["fg"] = "green"

NameError: name 'button1' is not defined

更新版本有望顯示整個圖片

該程序還有更多內容，所以才說第60行，但這是問題所在。 我試圖更改按下按鈕時的顏色。

Answer 1

最簡單的解決方法是在需要訪問該對象的兩個函數的開頭添加global button ：

def SP2T():
    global button1
    ...

def SW02():
    global button1
    ...

但是，使用global通常不是一個好兆頭-相反，您可以采用基於類的方法，如以下簡單示例所示：

import tkinter as tk

class MyGui(tk.Tk):

    def __init__(self):
        super(MyGui, self).__init__()
        self.create_widgets()


    def create_widgets(self):
        self.frame = tk.Frame(self)
        self.frame.pack()
        self.buttonA = tk.Button(self.frame, padx=13, pady=6, bd=4, text="SP2T",
                                 fg="black", command=self.SP2T)
        self.buttonA.pack(side=tk.LEFT)

    def SW02(self):
        print("SW02 is on")
        self.button1["fg"] = "green"

    def SP2T(self):
        self.button1 = tk.Button(self.frame, padx=13, pady=6, bd=4, text="SW02",
                                 fg="black", command=self.SW02)
        self.button1.pack(side=tk.LEFT)

if __name__ == "__main__":
    root = MyGui()
    root.mainloop()

Answer 2

您正在處理范圍問題。 在函數SW02()發生異常，因為您試圖修改不在函數范圍內的對象。 您需要傳遞它。將SW02()更改為以下內容：

def SW02(button1):
    print("SW02 is on")
    button1["fg"] = "green"

由於您將函數用作命令的動作，因此有一些選項可以將其實際傳遞。

使用lambda：

button1 = Button(frameSP2T, padx=13, pady = 6, bd=4, text="SW02",fg = "black", command = lambda: SW02(button1))

使用functools.partial：

from functools import partial
# other stuff
_SW02 = partial(SW02, button1)
button = Button(frameSP2T, padx=13, pady = 6, bd=4, text="SW02",fg="black", command=_SW02)

另外，按照jonrsharpe的回答中的建議，您可以將整個GUI函數重構為一個類，並使所有小部件成為類成員，然后將您的小部件操作與類方法而不是普通函數相關聯。 這樣，您修改GUI組件的所有功能都可以訪問它們。