Simple countdown programs to print "3, 2, 1, Action!" using while loop
Why does it has to be a while?

Maybe it is preference but for loops look cleaner.

Reversing can be done by using reversed function which reverses a iteration

countdown = 3
for count in reversed(range(1, countdown+1)):
    print(count)
print('action!')


Or you could use the step parameter in range(start, end, step) and rewrite the for loop to

for count in range(countdown, 0, -1):