/Demo/scripts/pi.py

 1#! /usr/bin/env python
 2
 3# Print digits of pi forever.
 4#
 5# The algorithm, using Python's 'long' integers ("bignums"), works
 6# with continued fractions, and was conceived by Lambert Meertens.
 7#
 8# See also the ABC Programmer's Handbook, by Geurts, Meertens & Pemberton,
 9# published by Prentice-Hall (UK) Ltd., 1990.
10
11import sys
12
13def main():
14    k, a, b, a1, b1 = 2L, 4L, 1L, 12L, 4L
15    while 1:
16        # Next approximation
17        p, q, k = k*k, 2L*k+1L, k+1L
18        a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
19        # Print common digits
20        d, d1 = a//b, a1//b1
21        while d == d1:
22            output(d)
23            a, a1 = 10L*(a%b), 10L*(a1%b1)
24            d, d1 = a//b, a1//b1
25
26def output(d):
27    # Use write() to avoid spaces between the digits
28    # Use str() to avoid the 'L'
29    sys.stdout.write(str(d))
30    # Flush so the output is seen immediately
31    sys.stdout.flush()
32
33if __name__ == "__main__":
34    main()