main.py

import PySimpleGUI as sg

def create_window(theme):
    sg.theme(theme)
    sg.set_options(
        font = 'Franklin 12', 
        button_element_size = (6, 3))

    button_size = (6, 3)

    layout = [
        [sg.Text('0', 
                 font = 'Franklin 26', 
                 justification = 'right', 
                 expand_x = True, 
                 pad = (10, 20),
                 right_click_menu = theme_menu,
                 key = '-TEXT-'
        )],
        #[sg.Push(), sg.Text('output', font = 'Franklin 26')],
        [sg.Button('C', expand_x = True), sg.Button('Enter', expand_x = True)],
        [sg.Button(7, size = button_size), sg.Button(8, size = button_size), sg.Button(9, size = button_size), sg.Button('*', size = button_size)],
        [sg.Button(4, size = button_size), sg.Button(5, size = button_size), sg.Button(6, size = button_size), sg.Button('/', size = button_size)],
        [sg.Button(1, size = button_size), sg.Button(2, size = button_size), sg.Button(3, size = button_size), sg.Button('-', size = button_size)],
        [sg.Button(0, expand_x = True), sg.Button('.', size = button_size), sg.Button('+', size = button_size)]
        ]
    return sg.Window('Calculadora', layout)

theme_menu = ['menu', ['LightGrey1', 'dark', 'DarkGray8', 'ramdom']]

window = create_window('LightGrey1')

current_num = []
full_operation = []
result = ''

while True:
    event, values = window.read()
    if event == sg.WIN_CLOSED:
        break

    if event in theme_menu[1]:
        window.close()
        window = create_window(event)

    if event in ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.']:
        current_num.append(event)
        num_string = ''.join(current_num)
        window['-TEXT-'].update(num_string)
    
    if event in ['+', '-', '/', '*']:
        full_operation.append(''.join(current_num))
        current_num = []
        full_operation.append(event)
        window['-TEXT-'].update(event)

    if event == 'Enter':
        if full_operation:
            try:
                full_operation.append(''.join(current_num))
                result = eval(' '.join(full_operation))
                window['-TEXT-'].update(result)
                current_num = list(map(str, str(result)))
                full_operation = []
            except:
                current_num = []
                full_operation = []
                result = []
                window['-TEXT-'].update('Err Math')  

        

    if event == 'C':
        current_num = []
        full_operation = []
        result = []
        window['-TEXT-'].update('0')     

window.close()