Python: Text Editor

from guizero import App, TextBox,Text, PushButton, Box, Slider, ButtonGroup

def fontsize():
    editor.text_size = sl_fontsize.value

def fontcolour():
    editor.text_color = bg_fontcolour.value

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

# function for writing files
def save_file():
    with open(file_name.value, "w") as f:
        f.write(editor.value)


app = App(title="My Text Editor in Python", width=640, height=480, layout="grid")
app.bg=(204,204,255)

# create a box to house the controls, we want the box to span the entire width of the app
file_controls = Box(app, align="left", height=20, width=560, grid=[0,0])

# create a TextBox for the file name
txt_filelabel=Text(file_controls,text="File Name: ",size=8, align="left")
file_name = TextBox(file_controls, text="example.txt", width=50, align="left")
file_name.bg=(255,255,255)

# create a TextBox which is not in the box and fills the rest of the GUI
editspace = Box(app, align="top", height=460, width=560, grid=[0,1])
editor = TextBox(editspace, multiline=True, height="fill", width="fill", scrollbar=True)
editspace.bg=(255,255,255)

# create a save button which uses the save_file function
buttonspace = Box(app, align="top", width=80, height=480, grid=[1,0,1,2])
save_button = PushButton(buttonspace, width=6, text="Save", command=save_file)
save_button.bg=(255,204,204)

# create an open button which uses the open_file function
open_button = PushButton(buttonspace, text="Open", width=6, command=open_file)
open_button.bg=(204,255,204)

# create a slider for font size
sl_fontsize = Slider(buttonspace,start=6,end=36,horizontal=False, command=fontsize)

# create a button group for text colour
bg_fontcolour = ButtonGroup(buttonspace, options=["Black", "Red", "Green", "Blue"], selected="Black", command=fontcolour)


app.display()