An unused variable takes up space in the code, and can lead to confusion, and it should be removed. If this variable is necessary, name the variable _ to indicate that it will be unused, or start the name with unused or _unused.

Bad practice

def update():
    for i in range(10): # Usused variable `i`
        time.sleep(0.01)
        display_result()

Preferred:

def update():
    for _ in range(10):
        time.sleep(0.01)
        display_result()