刚开始学习tkinter，试着做了个计算器，记录一些常用的函数和使用方法。

from tkinter import * #导入tkinter库
import re

root =Tk() #给窗体
root.title('calculator') #设置窗体名字
root.geometry('290x427')
root.resizable(width=False, height=False) ###固定窗体大小

c_width=9
c_height=3

frm=Frame(root,bg='white') #新建框架
frm.pack(expand = YES,fill = BOTH) #放置框架
display=StringVar()
e=Entry(frm,textvariable=display,font=("宋体",30,"normal"),width=9) #添加输入框
e.grid(row=0,column=0,rowspan=2,columnspan=4,sticky=W+N+E) #放置输入框位置

def insert_plus():
    e.insert(INSERT, '+')
def insert_minus():
    e.insert(INSERT, '-')
def insert_multiply():
    str_value = display.get()
    if str_value != "":
        e.insert(INSERT, '*')
def insert_divide():
    str_value = display.get()
    if str_value != "":
        e.insert(INSERT, '/')
def insert_equal():
    e.insert(INSERT,'=')

Button(frm,text='CE',width=c_width,height=c_height,bg='white',command= lambda :del_one_str(display)).grid(row=2,column=0,sticky=W) #设置按钮，lambda为匿名函数
Button(frm,text='C ',width=c_width,height=c_height,bg='white',command= lambda :display.set('')).grid(row=2,column=1)
Button(frm,text='<-',width=c_width,height=c_height,command= lambda :del_one_chr(display)).grid(row=2,column=2)

Button(frm,text='%',width=c_width,height=c_height,bg='white',command= lambda :calc_percent(display)).grid(row=3,column=0,sticky=W)
Button(frm,text='(',width=c_width,height=c_height,bg='white',command= lambda :e.insert(INSERT,'(')).grid(row=3,column=1)
Button(frm,text=')',width=c_width,height=c_height,bg='white',command= lambda :e.insert(INSERT,')')).grid(row=3,column=2)

Button(frm,text='1',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'1')).grid(row=4,column=0,sticky=W)
Button(frm,text='2',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'2')).grid(row=4,column=1)
Button(frm,text='3',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'3')).grid(row=4,column=2)

Button(frm,text='4',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'4')).grid(row=5,column=0,sticky=W)
Button(frm,text='5',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'5')).grid(row=5,column=1)
Button(frm,text='6',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'6')).grid(row=5,column=2)

Button(frm,text='7',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'7')).grid(row=6,column=0,sticky=W)
Button(frm,text='8',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'8')).grid(row=6,column=1)
Button(frm,text='9',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'9')).grid(row=6,column=2)

Button(frm,text='±',width=c_width,height=c_height,bg='yellow',command= lambda :negative(display)).grid(row=7,column=0,sticky=W)
Button(frm,text='0 ',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'0')).grid(row=7,column=2)
Button(frm,text='. ',width=c_width,height=c_height,bg='yellow',command= lambda :e.insert(INSERT,'.')).grid(row=7,column=1)

Button(frm,text='+',width=c_width,height=c_height,bg='white',command=insert_plus).grid(row=2,column=3,sticky=E)
Button(frm,text='-',width=c_width,height=c_height,bg='white',command=insert_minus).grid(row=3,column=3,sticky=E)
Button(frm,text='*',width=c_width,height=c_height,bg='white',command=insert_multiply).grid(row=4,column=3,sticky=E)
Button(frm,text='/',width=c_width,height=c_height,bg='white',command=insert_divide).grid(row=5,column=3,sticky=E)
Button(frm,text='=',width=c_width,height=c_height,bg='white',command= lambda :cal(display)).grid(row=6,column=3,sticky=N+S,rowspan=2)

def cal(display):
    str_value = display.get()
    if str_value != "":
        try:
            if "%" in str_value:
                str_value_change=str_value.replace("%","/100")
                value_tmp = eval(str_value_change)
                value=value_tmp
                if len(str(value_tmp)) > 16:
                    value="%e" % value_tmp
            else:
                value_tmp = eval(str_value) #eval:计算字符串表达式
                value = value_tmp
                if len(str(value_tmp)) > 16:
                    value = "%e" % value_tmp
            display.set("")
            e.insert(INSERT, value)
        except:
            display.set('')
            e.insert(INSERT, "para error")

def negative(display):
    str_value=display.get()
    if str_value != "" and ('-' not in str_value) and ('+' not in str_value) and ('*' not in str_value) and ('/' not in str_value):
        value = eval(display.get()) * (-1)
        display.set('')
        e.insert(INSERT,str(value))
    elif str_value != "" and "-" == str_value[0] and ('-' not in str_value[1:-1]) and ('+' not in str_value[1:-1]) and ('*' not in str_value[1:-1]) and ('/' not in str_value[1:-1]):
        value = eval(display.get()) * (-1)
        display.set('')
        e.insert(INSERT, str(value))
    else:
        e.insert(INSERT, '-')

def calc_percent(display):
    str_value=display.get()
    if str_value != "" and ('-' not in str_value) and ('+' not in str_value) and ('*' not in str_value) and ('/' not in str_value):
        value = eval(display.get()) / (100)
        display.set('')
        e.insert(INSERT,str(value))
    elif str_value != "" and "-" == str_value[0] and ('-' not in str_value[1:-1]) and ('+' not in str_value[1:-1]) and ('*' not in str_value[1:-1]) and ('/' not in str_value[1:-1]):
        value = eval(display.get()) / (100)
        display.set('')
        e.insert(INSERT, str(value))
    else:
        e.insert(INSERT, '%')

def del_one_chr(display):
    str_value = display.get()
    if str_value != "":
        display.set('')
        if "para error" == str_value or "para error" in str_value:
            display.set('')
        else:
            value = str_value[0:-1]
            e.insert(INSERT, str(value))

def del_one_str(display):
    str_value = display.get()
    value = ""
    if str_value != "":
        str_value_arr = re.split(r"[\+\-\*\/]+", str_value)
        value=str_value[0:len(str_value) - len(str_value_arr[-1])]
    display.set('')
    e.insert(INSERT, str(value))

root.mainloop() #让程序一直循环

运行效果：