I am first time using tkinter.Some error always show up when i execute this code. I just wanted a gui for a simple python project. errors are widgetName, self._w) + extra + self._options(cnf)) _tkinter.TclError: can't invoke "button" command: application has been destroyed
import tkinter
import os
MASTER = tkinter.Tk()
REVIEW_CONTENT_RAW = []
REVIEWS_SEL_FILM = []
def getReviewFileName(filmNum):
    basepath = os.path.abspath("..").split("/src")
    filepath = basepath[0] + "/resources/reviews"
    filename = filepath + "/review_film" + str(filmNum) +".txt";
    return filename
def loadReviewContents():
    global REVIEW_CONTENT
    for i in range(1,6):
        f = open(getReviewFileName(i), mode='r')
        fileContent = f.read().split("\n")
        REVIEW_CONTENT_RAW.append(fileContent)
def getFilmName(filmIndex):
    content = REVIEW_CONTENT_RAW[filmIndex]
    fTitle = content[0]
    return fTitle 
def getReviewListByMovie(filmIndex):
    reviewList = REVIEW_CONTENT_RAW[filmIndex]
    return reviewList
def setReviewsForSelectedFilm(filmIndex):
    global REVIEWS_SEL_FILM
    REVIEWS_SEL_FILM = getReviewListByMovie(filmIndex) 
def getReviewsForSelectedFilm():
    return REVIEWS_SEL_FILM
def populateUI():
    loadReviewContents()
    tkinter.Button(MASTER, text=getFilmName(0), 
                   command=buttonClickActionforFilm1).grid(row=1, column=0, sticky=tkinter.W, pady=4)
    tkinter.Button(MASTER, text=getFilmName(1), 
                   command=buttonClickActionforFilm2).grid(row=2, column=0, sticky=tkinter.W, pady=4)
    tkinter.Button(MASTER, text=getFilmName(2), 
                   command=buttonClickActionforFilm3).grid(row=3, column=0, sticky=tkinter.W, pady=4)
    tkinter.Button(MASTER, text=getFilmName(3), 
                   command=buttonClickActionforFilm4).grid(row=4, column=0, sticky=tkinter.W, pady=4)
    tkinter.Button(MASTER, text=getFilmName(4), 
                   command=buttonClickActionforFilm5).grid(row=5, column=0, sticky=tkinter.W, pady=4)
    tkinter.mainloop()
    return getReviewsForSelectedFilm()
def buttonClickActionforFilm1():
    global MASTER
    setReviewsForSelectedFilm(0)
    MASTER.destroy()
def buttonClickActionforFilm2():
    setReviewsForSelectedFilm(1)
    MASTER.destroy()
def buttonClickActionforFilm3():
    setReviewsForSelectedFilm(2)
    MASTER.destroy()
def buttonClickActionforFilm4():
    setReviewsForSelectedFilm(3)
    MASTER.destroy()
def buttonClickActionforFilm5():
    setReviewsForSelectedFilm(4)
    MASTER.destroy()
x = populateUI()
print(x)
 
    