I want to write a simple timer using tkinter.
I have a start button:

```
start_button = tkinter.Button(root, bg="white", text="Start", command=start_button_clicked)

```

and a command that runs on click

```
def start_button_clicked():
    start_button.config(text='Started', state='disabled')
    tm = timer.Timer()
    tm.count_time(1)

```

I expected it to 

1. Change button text and state
2. Create new Timer and run countdown

But in fact button parameters are changed only after the timer runs out.
Why it happens so and how can I change bu button right after click?