euler25.py

"""Euler 25

The Fibonacci sequence is defined by the recurrence relation:

Fn = Fn-1 + Fn-2 where F1 = 1 and F2 = 1
Hence the first 12 terms will be:

F1 = 1
F2 = 1
F3 = 2
F4 = 3
F5 = 5
F6 = 8
F7 = 13
F8 = 21
F9 = 34
F10 = 55
F11 = 89
F12 = 144
The 12th term, F12, is the first term to contain three digits.

What is the index of the first term in the Fibonacci sequence to contain 1000 digits?

"""
import math

def no_digits(num):
    """returns the number of digits in a number"""
    return int(math.log10(num)) + 1

def fibi():
    """Iterative Generator Fib sequence"""
    a, b = 0, 1
    while True:
        a, b = b, a + b
        yield a

# print list(x for x in fibi() if x >= 10 ** 1000)
for (index, x) in enumerate(fibi(), 1):
    print index, x

    if no_digits(x) >= 1000:
        print index
        break