lb.bind('<Control-Key-a>', lambda event: lb.tk.call('tk::ListboxSelectAll', lb))

lb.bind('<Control-Key-A>', lambda event: lb.event_generate('<<SelectAll>>'))

lb.bind_class(lb.winfo_class(), '<Control-Key-a>',
                    lambda event: lb.tk.call('tk::ListboxSelectAll', lb))

try:                        # In order to be able to import tkinter for
    import tkinter as tk    # either in python 2 or in python 3
except ImportError:
    import Tkinter as tk


if __name__ == '__main__':
    root = tk.Tk()
    lb = tk.Listbox(root)
    for i in range(4):
        lb.insert('end', i)

    lb.event_generate('<<SelectAll>>')
    #lb.bind('<Control-Key-a>',
    #                    lambda event: lb.tk.call('tk::ListboxSelectAll', lb))
    lb.bind_class(lb.winfo_class(), '<Control-Key-a>',
                        lambda event: lb.tk.call('tk::ListboxSelectAll', lb))
    lb['selectmode'] = 'asd'
    print(lb['selectmode'])
    lb.pack()
    tk.mainloop()