Text_app3.py

import tkinter
class Application(tkinter.Frame):
    def __init__ (self,master):
        tkinter.Frame.__init__(self,master)
        self.pack()
        self.CreateWidgets()
    def CreateWidgets(self):
        self.textbox1=tkinter.Text()
        self.textbox1.pack()
        self.button1=tkinter.Button()
        self.button1["command"]=self.button1_click
        self.button1["text"]="click"
        self.button1.pack()

        self.button2=tkinter.Button()
        self.button2["command"]=self.button1_save
        self.button2["text"]="save"
        self.button2.pack()

        self.button3=tkinter.Button()
        self.button3["command"]=self.button1_load
        self.button3["text"]="load"
        self.button3.pack()
        
    def button1_click(self):
        text=self.textbox1.get(0.0,tkinter.END)
        print(text.upper())
        print(text.lower())
        print(text.title())

    def button1_save(self):
        pass
    def button1_load(self):
        pass
    
root=tkinter.Tk()
app=Application(master=root)
app.mainloop()
root.destroy()