Tkinter一般是python自带的，所以代码不需要其他组件，本程序是在python2.7版本实现的。 

 主要涉及了tkinter的使用，函数定义和调用，匿名函数的使用，类成员函数定义等python基础知识，适合新手学习。

 代码如下：

from Tkinter import *

#创建横条型框架
def frame(root, side):
    w = Frame(root)
    w.pack(side = side, expand = YES, fill = BOTH)
    return w
#创建按钮
def button(root, side, text, command = None):
    w = Button(root, text = text, command = command)
    w.pack(side = side, expand = YES, fill = BOTH)
    return w
#继承了Frame类，初始化程序界面的布局
class Calculator(Frame):
    def __init__(self):
        
        Frame.__init__(self)
        
        self.pack(expand = YES, fill = BOTH)
        self.master.title('Simple Calculater')
        
        display = StringVar()
        #添加输入框
        Entry(self, relief = SUNKEN,
              textvariable = display).pack(side = TOP, expand = YES,
                                           fill = BOTH)
		#添加横条型框架以及里面的按钮
        for key in('123', '456', '789', '-0.'):
            keyF = frame(self, TOP)
            for char in key:
                button(keyF, LEFT, char, lambda w = display, c = char:w.set(w.get() + c))
		#添加操作符按钮
        opsF = frame(self, TOP)
        for char in '+-*/=':
            if char == '=':
                btn = button(opsF, LEFT, char)
                btn.bind('<ButtonRelease - 1>', lambda e, s = self, w = display:s.calc(w), '+')

            else:
                btn = button(opsF, LEFT, char, lambda w = display, s = '%s' %char:w.set(w.get() + s))
		#添加清除按钮
        clearF = frame(self, BOTTOM)
        button(clearF, LEFT, 'clear', lambda w = display:w.set(''))

	#调用eval函数计算表达式的值
    def calc(self, display):
        try:
            display.set(eval(display.get()))
        except:
            display.set("ERROR")
#程序的入口
if __name__ == '__main__':
    print('ok')
    Calculator().mainloop()