参考 PyDataMath-II。

先创建计算器的 Window：

import numpy as np
import PySimpleGUI as sg 

# 字体设置
font_name = 'Franklin Gothic Book'

# 设置 Button 的配置
button_font = (font_name, 24)
bw = {'size':(7,2), 'font':button_font, 'button_color':("black","#F8F8F8")}
bt = {'size':(7,2), 'font':button_font, 'button_color':("black","#F1EABC")}
bo = {'size':(31,2), 'font':button_font, 'button_color':("black","#ECA527"), 'focus':True}
# 定义布局
layout = [
    [sg.Text('计算器', size=(50,1), justification='right', background_color="#272533", 
            text_color='white', font=(font_name, 14, 'bold'))],
    [sg.Text('0.0000', size=(18,1), justification='right', background_color='black', 
            text_color='red', font=('Digital-7',48), relief='sunken', key="_DISPLAY_")]
]
layout += [[sg.Button(str(name),**bw) for name in names] 
           for names in np.arange(1, 10).reshape((3,3))]
layout[-1] += [sg.Button("*",**bt)]
layout[-2] += [sg.Button("-",**bt)]
layout[-3] += [sg.Button("+",**bt)]
layout += [[sg.Button('0',**bw), sg.Button('.',**bw), 
            sg.Button('C',**bt), sg.Button('/',**bt)],
            [sg.Button('=',**bo, bind_return_key=True)]]
# 创建 Window
window = sg.Window('Python 定制的计算器', layout=layout,
                   background_color="#272533",  return_keyboard_events=True)

接着定义一些辅助函数：

# helper functions
def format_number():
    '''create a consolidated string of numbers from front and back lists'''
    return float(''.join(var['front']) + '.' + ''.join(var['back']))

def update_display(display_value):
    '''update the calculator display after an event click'''
    try:
        window['_DISPLAY_'].update(value='{:,.4f}'.format(display_value))
    except:
        window['_DISPLAY_'].update(value=display_value)

# click events
def number_click(event):
    '''number button button click event '''
    global var
    if var['decimal']:
        var['back'].append(event)
    else:
        var['front'].append(event)
    update_display(format_number())
    
def clear_click():
    '''C button click event '''
    global var
    var['front'].clear()
    var['back'].clear()
    var['decimal'] = False 

def operator_click(event):
    ''' + - / * button click event '''
    global var
    var['operator'] = event
    try:
        var['x_val'] = format_number()
    except:
        var['x_val'] = var['result']
    clear_click()

def calculate_click():
    ''' equals button click event '''
    global var
    var['y_val'] = format_number()
    try:
        var['result'] = eval(str(var['x_val']) + var['operator'] + str(var['y_val']))
        update_display(var['result'])
        clear_click()    
    except:
        update_display("ERROR! DIV/0")
        clear_click()

最后，启动 GUI 界面：

var = {'front':[], 'back':[], 'decimal':False,
       'x_val':0.0, 'y_val':0.0, 'result':0.0, 'operator':''}

while True:
    event, values = window.read()
    if event == None:
        break
    elif event in np.arange(10).astype('str'):
        number_click(event)
    elif event in ['Escape:27','C']: # 'Escape:27 for keyboard control
        clear_click()
        update_display(0.0)
        var['result'] = 0.0
    elif event in ['+','-','*','/']:
        operator_click(event)
    elif event == '=':
        calculate_click()
    elif event == '.':
        var['decimal'] = True
    elif event == '%':
        update_display(var['result'] / 100.0)
        
window.close()

最终的效果图：

计算器界面