from tkinter import *
from tkinter import ttk

import json


def save(*args):
    if pupil.get() == '':
        return pupil_entry.focus()
    if labs.get() == '':
        return labs_entry.focus()

    data = read_json()
    data[pupil.get()] = labs.get().split()

    write_json(data)

    pupil.set('')
    labs.set('')


def clear_data():
    with open(FILENAME, 'w') as f:
        f.write('')


def write_json(data):
    with open(FILENAME, 'w') as f:
        json.dump(data, f, indent=2, ensure_ascii=False)


def read_json():
    with open(FILENAME) as f:
        if f.readline() == '':
            return {}
        return json.load(f)


FILENAME = 'data.json'


root = Tk()

mainframe = ttk.Frame(root, padding='10')
mainframe.grid(row=0, column=0)

pupil = StringVar()
labs = StringVar()

pupil_entry = ttk.Entry(mainframe, textvariable=pupil)
pupil_entry.grid(row=0, column=1)
pupil_entry.focus()
labs_entry = ttk.Entry(mainframe, textvariable=labs)
labs_entry.grid(row=1, column=1)

ttk.Label(mainframe, text='Ученик: ').grid(row=0, column=0)
ttk.Label(mainframe, text='Выполненные работы: ').grid(row=1, column=0)

ttk.Button(mainframe, text='Очистить', command=clear_data).grid(row=2, column=0)
ttk.Button(mainframe, text='Сохранить', command=save).grid(row=2, column=1)

for child in mainframe.winfo_children():
    root.bind('<Return>', save)


if __name__ == '__main__':
    root.mainloop()