循环创建同名tk.Button时，如何为命令绑定不同参数？

问题场景 #

通过for循环批量创建Tkinter按钮时，按钮显示的品牌名称正确，但点击任意按钮，回调函数接收的参数始终是循环最后一次的取值（如示例中的TCL），无法实现点击对应品牌按钮输出对应内容（比如点击GE按钮输出"This is GE"）。

原始问题代码 #

import tkinter as tk
from tkinter import Button

root = tk.Tk()
root.title("Root")
root.configure(bg = "#333333")   
root.geometry("600x500")          
root.resizable(False, False) 

# 补充原代码缺失的frame定义，保证代码可运行
frame = tk.Frame(root, bg="#333333")
frame.pack(fill="both", expand=True)

def Category(category):
    y = 40
    category_list = [['Refrigerator', 'Refrigerator', 'Refrigerator', 'Refrigerator', 'Refrigerator', 'Television', 'Television', 'Television', 'Television', 'Television'], ['GE', 'LG', 'Maytag', 'Samsung', 'Whirlpool', 'Hisense', 'LG', 'Samsung', 'Sony', 'TCL']]
    category_item = category_list[0]
    brand = category_list[1]
    for x in range(len(category_item)):
        if category_item[x] == category:
            if category == "Television":
                brand_button = Button(frame, text = brand[x], font = "Poppins, 10", bg = "#222222", fg = "#ffffff", width = 12, borderwidth = 0, highlightthickness = 0, activebackground = "#222222", activeforeground = "#ffffff", anchor = "w")
                brand_button.bind("<Button-1>", lambda e:getTV(brand[x]))
                brand_button.place(x = 40, y = y)
                y += 35
            else:
                brand_button = Button(frame, text = brand[x], font = "Poppins, 10", bg = "#222222", fg = "#ffffff", width = 12, borderwidth = 0, highlightthickness = 0, activebackground = "#222222", activeforeground = "#ffffff", anchor = "w")
                brand_button.bind("<Button-1>", lambda e:getFridge(brand[x]))
                brand_button.place(x = 40, y = y)
                y += 35

def getFridge(user_input):
    record = ['LG', 'GE', 'Maytag', 'Samsung', 'Whirlpool']
    for row in record:
        if user_input == row:
            print("This is", row)

def getTV(user_input):
    record = ['Hisense', 'LG', 'Samsung', 'Sony', 'TCL']
    for row in record:
        if user_input == row:
            print("This is", row)

Category("Refrigerator")
root.mainloop()

问题原因 #

这是lambda表达式的延迟绑定特性导致的：lambda内部的brand[x]不会在循环迭代时立即计算取值，而是等到按钮被点击触发回调时，才会去获取变量x的当前值。而循环结束后，x已经指向最后一次迭代的索引，因此所有按钮的回调都会使用同一个参数值。

修改后的代码 #

只需修改绑定lambda的部分，通过默认参数提前固定当前循环的品牌值：

import tkinter as tk
from tkinter import Button

root = tk.Tk()
root.title("Root")
root.configure(bg = "#333333")   
root.geometry("600x500")          
root.resizable(False, False) 

frame = tk.Frame(root, bg="#333333")
frame.pack(fill="both", expand=True)

def Category(category):
    y = 40
    category_list = [['Refrigerator', 'Refrigerator', 'Refrigerator', 'Refrigerator', 'Refrigerator', 'Television', 'Television', 'Television', 'Television', 'Television'], ['GE', 'LG', 'Maytag', 'Samsung', 'Whirlpool', 'Hisense', 'LG', 'Samsung', 'Sony', 'TCL']]
    category_item = category_list[0]
    brand = category_list[1]
    for x in range(len(category_item)):
        if category_item[x] == category:
            if category == "Television":
                brand_button = Button(frame, text = brand[x], font = "Poppins, 10", bg = "#222222", fg = "#ffffff", width = 12, borderwidth = 0, highlightthickness = 0, activebackground = "#222222", activeforeground = "#ffffff", anchor = "w")
                # 添加默认参数b=brand[x]，提前绑定当前循环的品牌值
                brand_button.bind("<Button-1>", lambda e, b=brand[x]: getTV(b))
                brand_button.place(x = 40, y = y)
                y += 35
            else:
                brand_button = Button(frame, text = brand[x], font = "Poppins, 10", bg = "#222222", fg = "#ffffff", width = 12, borderwidth = 0, highlightthickness = 0, activebackground = "#222222", activeforeground = "#ffffff", anchor = "w")
                # 同样通过默认参数绑定当前品牌值
                brand_button.bind("<Button-1>", lambda e, b=brand[x]: getFridge(b))
                brand_button.place(x = 40, y = y)
                y += 35

def getFridge(user_input):
    record = ['LG', 'GE', 'Maytag', 'Samsung', 'Whirlpool']
    for row in record:
        if user_input == row:
            print("This is", row)

def getTV(user_input):
    record = ['Hisense', 'LG', 'Samsung', 'Sony', 'TCL']
    for row in record:
        if user_input == row:
            print("This is", row)

Category("Refrigerator")
root.mainloop()

核心修改说明 #

在lambda表达式中新增一个带默认值的参数（如b=brand[x]）：

• Python的函数默认参数会在函数定义时求值，而非调用时。
• 循环每迭代一次，都会创建一个新的lambda，并把当前循环的brand[x]值赋值给默认参数b，相当于把当前品牌值“固定”在这个lambda里。
• 当按钮被点击时，lambda会使用提前绑定好的b值作为参数传递给回调函数，从而实现点击对应按钮输出对应品牌内容的效果。

内容的提问来源于stack exchange，提问作者Ferdinand Jacques