问错误：_tkinter.TclError:无法调用"wm“命令:应用程序已被销毁

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#file1
class GetInfo1():
    def getInfo1():
        #my code
        return info1
#file2
 class GetInfo2():
    def getInfo2():
        #my code
        return info2
 #file3
 class GetInfo3():
    def getInfo3():
        #my code
        return info3

from GetInfo1 import *
from GetInfo2 import *
from GetInfo3 import *

object1 = GetInfo1()
getInfor1 = object1.getInfo1()
print getInfor1

object2 = GetInfo2()
getInfor2 = object2.getInfo2()
print getInfor2

object3 = GetInfo3()
getInfor3 = object3.getInfo3()
print getInfor3

from Tkinter import *

root = Tk()
app = Frame(root)

entry = Entry(app)
entry.grid()


class GetInfo1():

def OnClick(self):
    global input1
    input1 = entry.get()
    #print ("You have entered %s"%input1)
    root.destroy()
    return input1

def getInfo1(self):

    '''Window'''
    global input1
    root.title("Input Permutation Range ")
    root.geometry("300x200")
    app.grid()
    label = Label (app, text="Please Enter the propogation range ( 2 - 4)")
    label.grid()

    '''Button'''
    Object2 = AskPermutationRange()
    button = Button (app, text="Submit", command=Object2.OnClick)
    button.grid()
    root.focus_set()
    root.mainloop()
    return input1