Question

I need a code that calculates nth fibonacci number as well as giving me the time used to calculate it, in python.

def fib(n):
    if n==0 or n==1: return 1
    else: return fib(n-1)+fib(n-2)

The calculation of the number step must use a such method.

Answer 1

Use the timeit module to time the function:

import timeit

def fib(x):
    if x==0 or x==1: return 1
    else: return fib(x-1)+fib(x-2)

print timeit.Timer('fib(5)', 'from __main__ import fib').timeit()

Output:

3.12172317505

To directly answer the question in the title, you can use time.time() to get the current time since the epoch in seconds and keep calculating the subsequent fibonacci number until the time limit is reached. I’ve chosen to use an efficient method of computing fibonacci numbers below to give you a better demonstrating of this concept.

def fibTimeLimited(limit):
  start = time.time()
  n, f0, f1 = 1, 0, 1
  while time.time() < start + limit:
    n += 1
    f0, f1 = f1, f0+f1
  return (n, f1)

Sample output:

Calculated 1st fibonacci number as 1 in 0.000001 seconds
Calculated 31st fibonacci number as 1346269 in 0.000010 seconds
Calculated 294th fibonacci number as 12384578529797304192493293627316781267732493780359086838016392 in 0.000100 seconds