if statement - Python: How to keep running program until some value becomes 0 and checking how long it takes -

i have following code:

time_counter = 0 in range(time_counter):     if pred > 0:         prey, pred = prey*(1+a-b*pred), pred*1-c+d*prey)     else:         print time_counter     time_counter +=1 

the values a, b, c, , d fixed 0.1, 0.01, 0.01, 0.00009. pred 20 , prey 1000. i'm trying figure out how long takes pred become 0 (as integer, not float) , display time.

logically, can think of starting time @ 0 , running formula...if pred greater 0 repeat , until pred 0 or less 0 stop , display time. not sure doing wrong.

please try keep basic. i'd able using loop conditional statements , using python 2.7 syntax.

edit: sorry if confusing. want count time periods (which in case number of iterations) loop runs until pred equal 0. however, pred should considered 0 once < 1 0.999 0.

here's sloppy answer mobile:

import time  time.time() while (pred > 0):     # smooth jazz time.time() 

apologies if kind of answer bit lacking don't have ide available verify syntax.