Flypi2 (pi algorithme)

#!/usr/bin/env python
from __future__ import with_statement
import decimal

def pi():
    D = decimal.Decimal
    with decimal.localcontext() as pop:
        pop.prec += 2
        pip = lambda am,x,r: (am + x)**2 / (4 * r)
        am, x, r, o = 1, 1/D(2).sqrt(), 1/D(4), 1
        pi, pif = pip(am, x, r), None
        while pi != pif:
            pif = pi
            an = (am + x) / 2
            x = (am * x).sqrt()
            r -= o * (am - an)**2
            am, o = an, 2*o
            pi = pip(am, x, r)
    return +pi

decimal.getcontext().prec = input("le nombre de chiffre en tout : ")
print pi()