FutureLearn GUIZero - Text Editor Open Save Buttons

from guizero import App, TextBox, PushButton, Box, Combo, Slider

# Functions
def open_file():
    with open(file_name.value, "r") as f:
        editor.value = f.read()
    open_button.hide()

def save_file():
    with open(file_name.value, "w") as f:
        f.write(editor.value)
    save_button.hide()

def enable_save():
    save_button.enable()
    save_button.show()
    enable_open()

def enable_open():
    open_button.enable()
    open_button.show()

def change_font():
    editor.font = font.value

def change_text_size():
    editor.text_size = size.value
    editor.resize(1, 1)
    editor.resize("fill", "fill")

def change_font_colour():
    editor.text_color = font_colour.value

app = App(title="Text Editor")


# Lower box and widgets
preferences_controls = Box(app, align="top", width="fill", border=True)
font = Combo(preferences_controls, options=["courier", "stencil", "times new roman", "verdana"], align="left", command=change_font)
size = Slider(preferences_controls, align="left", command=change_text_size, start=10, end=18)
font_colour = Combo(preferences_controls, align="left", command=change_font_colour, options=["black", "blue", "green", "orange", "red", "yellow"])

editor = TextBox(app, multiline=True, height="fill", width="fill", command=enable_save)

# Top box and widgets
file_controls = Box(app, align="top", width="fill")
file_name = TextBox(file_controls, text="text_file.txt", width=50, align="left")
save_button =PushButton(file_controls, text="Save", command=save_file, align="right", enabled=False)
open_button = PushButton(file_controls, text = "Open", command=open_file, align="right")


app.display()