microbit_shake_timer.py

from microbit import *

# State: 0 if on standby (waiting for button), 1 if active (waiting for shake)
state = 0
# The time button A was pressed, in milliseconds
last_press = 0

# Target image on display means it's in standby state, stick figure image on display means it's in active state
display.show(Image.TARGET)

# Infinite loop? 
while True:
  # Registers button A press if and only if state is 0 (standby)
  if state == 0 and button_a.is_pressed():
    # Set state to 1 (active)
    state = 1
    
    # Record start time
    last_press = running_time()
    
    # Since state is now 1, update display image to stick figure 
    display.show(Image.STICKFIGURE)
  
  # Registers shake gesture if and only if state is 1 (active)
  elif state == 1 and accelerometer.is_gesture("shake"):
    # Set state to 0 (standby)
    state = 0
    
    # Record end time and display time difference
    end_time = running_time()
    difference = end_time - last_press
    display.scroll("%.3f sec" % (difference / 1000.0))
    
    # Since state is now 0, update display image to target
    display.show(Image.TARGET)

# Since there is an infinite loop, the code never gets here.
# Below code is optional (but preferred)
display.scroll("PIZZA TACOS PIZZA TACOS HA HA LOL")
display.show(Image.COW)