euler025.py

def euler25():
    """http://projecteuler.net/problem=25

    The Fibonacci sequence is defined by the recurrence relation:

    Fn = Fn1 + Fn2, 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 first term in the Fibonacci sequence to contain 1000 digits?
    """
    f1, f2, term = 2, 1, 3
    while f1 < 10 ** 999:
        f1, f2, term = f1 + f2, f1, term + 1
    return term