Int Variables in different Tkinter windows only returning 0

[harry76]

I have checkboxes in a secondary tkinter window (not root) that only return an IntVar of 0 even when selected. This is not a problem in the main window.

I have the code working in the main root window and when selected, the checkboxes return 1 and not 0, however when using the exact same code in a separate tkinter window it returns only 0's. I have added window2.mainloop() at the end which did nothing.

button_list = []              #create list to hold checkbox values
def done_press():           #what to do when done button pressed
    for x in range(len(data)):
        print(button_list[x].get())
play = Tk()                #second window called play
row=[1,2,3,4,5,6,7,8,9]                             
Label(play, text='Whats on').grid(row=0, column=0, padx=30, pady=20, columnspan=3)
for box in range(len(data)):    #create checkboxes
    button_list.append(IntVar())   #append checkbox list for each selected 
    button = Checkbutton(play, text=data[box], variable=button_list,)  
    button.grid(column=0,row=row[box], pady=5, padx=30)
done = Button(play, text='Done', command=done_press)
done.grid(column=0,row=11, columnspan=2)
play.mainloop()

any help would be appreciated, thanks.