编写Python代码并标明详细注释和解释，编写GUI计算器应用程序，实现简单的算术运算功能。

好的，下面是代码和注释：

from tkinter import *

# 创建 GUI 应用程序窗口
root = Tk()
root.title("简易计算器")

# 创建一个文本框用于显示输入和输出
text = Entry(root, width=35, borderwidth=5)
text.grid(row=0, column=0, columnspan=4, padx=10, pady=10)

# 定义操作函数
def button_click(number):
    # 清除文本框原有内容
    text.delete(0, END)
    # 在文本框中插入新的内容
    text.insert(0, str(number))

def button_add():
    # 获取文本框中的内容
    first_number = text.get()
    # 清除文本框原有内容
    text.delete(0, END)
    # 保存第一个数以备后续计算
    global f_num
    f_num = int(first_number)
    # 设置运算符
    global math
    math = "addition"

def button_subtract():
    # 获取文本框中的内容
    first_number = text.get()
    # 清除文本框原有内容
    text.delete(0, END)
    # 保存第一个数以备后续计算
    global f_num
    f_num = int(first_number)
    # 设置运算符
    global math
    math = "subtraction"

def button_multiply():
    # 获取文本框中的内容
    first_number = text.get()
    # 清除文本框原有内容
    text.delete(0, END)
    # 保存第一个数以备后续计算
    global f_num
    f_num = int(first_number)
    # 设置运算符
    global math
    math = "multiplication"

def button_divide():
    # 获取文本框中的内容
    first_number = text.get()
    # 清除文本框原有内容
    text.delete(0, END)
    # 保存第一个数以备后续计算
    global f_num
    f_num = int(first_number)
    # 设置运算符
    global math
    math = "division"

def button_equal():
    # 获取文本框中的内容
    second_number = text.get()
    # 清除文本框原有内容
    text.delete(0, END)

    if math == "addition":
        # 计算结果
        text.insert(0, f_num + int(second_number))
    elif math == "subtraction":
        # 计算结果
        text.insert(0, f_num - int(second_number))
    elif math == "multiplication":
        # 计算结果
        text.insert(0, f_num * int(second_number))
    elif math == "division":
        # 计算结果
        text.insert(0, f_num / int(second_number))

def button_clear():
    # 清除文本框原有内容
    text.delete(0, END)

# 创建按钮
button_1 = Button(root, text="1", padx=40, pady=20, command=lambda: button_click(1))
button_2 = Button(root, text="2", padx=40, pady=20, command=lambda: button_click(2))
button_3 = Button(root, text="3", padx=40, pady=20, command=lambda: button_click(3))
button_4 = Button(root, text="4", padx=40, pady=20, command=lambda: button_click(4))
button_5 = Button(root, text="5", padx=40, pady=20, command=lambda: button_click(5))
button_6 = Button(root, text="6", padx=40, pady=20, command=lambda: button_click(6))
button_7 = Button(root, text="7", padx=40, pady=20, command=lambda: button_click(7))
button_8 = Button(root, text="8", padx=40, pady=20, command=lambda: button_click(8))
button_9 = Button(root, text="9", padx=40, pady=20, command=lambda: button_click(9))
button_0 = Button(root, text="0", padx=40, pady=20, command=lambda: button_click(0))

button_add = Button(root, text="+", padx=39, pady=20, command=button_add)
button_subtract = Button(root, text="-", padx=41, pady=20, command=button_subtract)
button_multiply = Button(root, text="*", padx=40, pady=20, command=button_multiply)
button_divide = Button(root, text="/", padx=41, pady=20, command=button_divide)

button_equal = Button(root, text="=", padx=91, pady=20, command=button_equal)
button_clear = Button(root, text="清除", padx=79, pady=20, command=button_clear)

# 放置按钮
button_1.grid(row=1, column=0)
button_2.grid(row=1, column=1)
button_3.grid(row=1, column=2)

button_4.grid(row=2, column=0)
button_5.grid(row=2, column=1)
button_6.grid(row=2, column=2)

button_7.grid(row=3, column=0)
button_8.grid(row=3, column=1)
button_9.grid(row=3, column=2)

button_0.grid(row=4, column=0)

button_add.grid(row=5, column=0)
button_subtract.grid(row=6, column=0)
button_multiply.grid(row=6, column=1)
button_divide.grid(row=6, column=2)

button_equal.grid(row=5, column=1, columnspan=2)
button_clear.grid(row=4, column=1, columnspan=2)

# 运行应用程序窗口
root.mainloop()

这段代码实现了一个简单的计算器应用程序，包括数字按钮、运算符按钮、等号按钮和清除按钮。用户可以在文本框中输入数字，并使用运算符按钮进行加、减、乘、除运算。按下等号按钮将计算结果显示在文本框中。按下清除按钮将清除文本框的内容。