How to check if window is fullscreen or not

[delphinis]

Hi,
trying to play with fullscreen, to save the last configuration of the screen, i whanted to obtain the info if the window is in fullscreen or not. But nothing works.
I tried with
- .attributes('fullscreen') => this always results in 0
- .wm_state('zoomed') => this doesn'r return a value, or more exact: {str}''

How to check if the window is zoomed or fullscreen?
Working with windows.

Here's my (reduced) code:

try:
    import tkinter as tk
except ImportError:
    import Tkinter as tk

class Window(tk.Frame):
    #def __init__(self, master, **kwargs):
    def __init__(self, master):
        self.master = master
        self.master.bind("<F11>", self.do_fullscreen)
        self.master.bind("<Escape>", self.end_fullscreen)
        self.master.geometry("400x500+0+0")

    def do_fullscreen(self, event=None):
        self.master.wm_state('zoomed')
        #fullscreen = self.master.attributes('-fullscreen')
        fullscreen = self.master.wm_state('zoomed')
        self.master.title('fullscreen=' + str(fullscreen))

    def end_fullscreen(self, event=None):
        self.master.wm_state('normal')
        #fullscreen = self.master.attributes('-fullscreen')
        fullscreen = self.master.wm_state('zoomed')
        self.master.title('fullscreen=' + str(fullscreen))

if __name__ == "__main__":
    root = tk.Tk()
    frame = Window(root)
    root.mainloop()

Note that storing the info in a variable is no option, because other events outside of <F11> and <Escape> can change the window, p.e. clicking on the head of the window and drag it down when fullscreen, is changing the window to 'normal'