def fio():
    sur = input("Введите фамилию: ")
    name = input("Введите имя: ")
    middle = input("Введите отчество: ")
    
    return f'{sur} {name[0]}. {middle[0]}.'.title()
 
print(fio())

import tkinter as tk
from tkinter import messagebox

def get_short_FIO():
    surname = entry_surname.get().capitalize()
    name = entry_name.get().capitalize()
    patronymic = entry_patronymic.get().capitalize()

    short_fio = surname + " " + name[0] + "." + patronymic[0] + "."
    label_result.config(text="Сокращенная форма записи ФИО: " + short_fio)

window = tk.Tk()
window.title("Сокращенная форма ФИО")

label_surname = tk.Label(window, text="Фамилия:")
label_surname.pack()
entry_surname = tk.Entry(window)
entry_surname.pack()

label_name = tk.Label(window, text="Имя:")
label_name.pack()
entry_name = tk.Entry(window)
entry_name.pack()

label_patronymic = tk.Label(window, text="Отчество:")
label_patronymic.pack()
entry_patronymic = tk.Entry(window)
entry_patronymic.pack()

button_get_short_fio = tk.Button(window, text="Получить сокращенную форму ФИО", command=get_short_FIO)
button_get_short_fio.pack()

label_result = tk.Label(window, text="")
label_result.pack()

window.mainloop()