Counter loop with multiplier from input

i have been having lot of problems trying to get this to work, basically what i want is:

import time
while True:
x = 1
print(x+= multi)
time.sleep(0.5)

if KeyPressed
multi = int(input("what Multiplier: "))
restart loop

i know this does not work, it is just to give you an idea of what im trying to do, any help would be appreciated. Thanks.