Calculate Pi using the Leibniz formula

gistfile1.py

def gen_pi():
    denom = 1.
    positive = True
    value = 0.
    while True:
        value += (1. / denom) if positive else -(1. / denom)
        denom += 2.
        positive = not positive
        yield 4. * value

gen = gen_pi()
import sys
for i in xrange(int(sys.argv[1])):
    pi = gen.next()

print pi