import tkinter as tk
root = tk.Tk()
handler_called = False
x = y = 0

def prt():
    global handler_called
    print('handler called')  # for this demo only, not in unittest
    handler_called = True
def ev(e):
    global x, y
    print(e.x, e.y)  # see comment above
    x, y = e.x, e.y
    
button = tk.Button(root, text='Click', command=prt)
# button command fires when button is released
button.place(x=20, y=20)
button.bind('<ButtonPress-1>', ev)
button.update()  # required for following
button.event_generate('<ButtonPress-1>', x=1, y=1)  # changes x,y.
assert x == y == 1
button.event_generate('<ButtonRelease-1>', x=1, y=1)  # does not fire command
assert handler_called == False
button.invoke()  # does fire command
assert handler_called == True

etext = tk.StringVar('')
entry=tk.Entry(root, textvariable=etext)
entry.place(x=20, y=50)
entry.focus_force()  # required for text entry
entry.update()
entry.event_generate('<Key-a>')  # inserts 'a'
# Can Use .insert or a string varible to insert or set multiple chars,
# but keys like 'Home' have no text equivalent.
assert entry.get() == 'a'
assert etext.get() == 'a'
entry.insert('insert', 'bc')
assert entry.get() == 'abc'
etext.set('def')
assert etext.get() == 'def'