from tkinter import *  
    reset=True  
    def buttonCallBack(event):  
        global label  
        global reset  
        num=event.widget['text']  
        if num=='C':  
            label['text']="0"  
            return  
        if num in "=":  
            label['text']=str(eval(label['text']))  
            reset=True  
            return   
        s=label['text']  
        if s=='0' or reset==True:  
            s=""  
            reset=False  
        label['text']=s+num  
    #主窗口  
    root=Tk()  
    root.wm_title("计算器")  
    #显示栏1  
    label=Label(root,text="0",background="white",anchor="e")  
    label['width']=35  
    label['height']=2  
    label.grid(row=1,columnspan=4,sticky=W)  
    #按钮  
    showText="789/456*123-0.C+"  
    for i in range(4):  
        for j in range(4):  
            b=Button(root,text=showText[i*4+j],width=7)  
            b.grid(row=i+2,column=j)  
            b.bind("<Button-1>",buttonCallBack)  
    showText="()"  
    for i in range(2):  
        b=Button(root,text=showText[i],width=7)  
        b.grid(row=6,column=2+i)  
        b.bind("<Button-1>",buttonCallBack)  
    b=Button(root,text="=")  
    b.grid(row=6,columnspan=2,sticky="we")  
    b.bind("<Button-1>",buttonCallBack)  
    root.mainloop()  

来自：http://blog.csdn.net/ccy0815ccy/article/details/42426373