editor.py

#!/usr/bin/python3

from guizero import App, TextBox, PushButton, Box
from tkinter import filedialog

def OpenFile():
    filepath = filedialog.askopenfilename()
    file_name.value = filepath
    f = open(filepath,"r")
    editor.value = f.read()
    f.close()

def SaveFile():
    filepath = filedialog.asksaveasfile()
    if filepath:
        f = open(filepath.name,"w")
        f.write(editor.value)
        f.close()


app = App(title="texteditor")

# create a box to house the controls, we want the box to span the entire width of the app
file_controls = Box(app, align="top", width="fill")

# create a TextBox for the file name
file_name = TextBox(file_controls, text="text_file.txt", width=32, align="left")

# create a save button which uses the save_file function
save_button = PushButton(file_controls,text="Save",align="right",command=SaveFile)

# create an open button which uses the open_file function
open_button = PushButton(file_controls,text="Open",align="right",command=OpenFile)

# create a TextBox which is not in the box and fills the rest of the GUI
editor = TextBox(app, multiline=True, height="fill", width="fill")

app.display()