another Python π calculator

pidigits.py

"""
Calculate digits of pi. This module can be run interactively with

    python pidigits.py

"""
__docformat__ = 'plaintext'

import sys
import math
from time import clock

from mpmath.libmp import bin_to_radix, numeral, pi_fixed

def display_fraction(digits, skip=0, colwidth=10, columns=5):
    perline = colwidth * columns
    printed = 0
    for linecount in range((len(digits)-skip) // (colwidth * columns)):
        line = digits[skip+linecount*perline:skip+(linecount+1)*perline]
        for i in range(columns):
            print line[i*colwidth : (i+1)*colwidth],
        print ":", (linecount+1)*perline
        if (linecount+1) % 10 == 0:
            print
        printed += colwidth*columns
    rem = (len(digits)-skip) % (colwidth * columns)
    if rem:
        buf = digits[-rem:]
        s = ""
        for i in range(columns):
            s += buf[:colwidth].ljust(colwidth+1, " ")
            buf = buf[colwidth:]
        print s + ":", printed + colwidth*columns

def calculateit(base, n, tofile):
    intpart = numeral(3, base)
    skip = 1
    if base <= 3:
        skip = 2

    prec = int(n*math.log(base,2))+10

    print "Step 1 of 2: calculating binary value..."
    t = clock()
    a = pi_fixed(prec, verbose=True, verbose_base=base)
    step1_time = clock() - t

    print "Step 2 of 2: converting to specified base..."
    t = clock()
    d = bin_to_radix(a, prec, base, n)
    d = numeral(d, base, n)
    step2_time = clock() - t

    print "\nWriting output...\n"

    if tofile:
        out_ = sys.stdout
        sys.stdout = tofile
    print "%i base-%i digits of pi:\n" % (n, base)
    print intpart, ".\n"

    display_fraction(d, skip, colwidth=10, columns=5)
    if tofile:
        sys.stdout = out_
    print "\nFinished in %f seconds (%f calc, %f convert)" % \
        ((step1_time + step2_time), step1_time, step2_time)

def interactive():
    print "Compute digits of pi with mpmath\n"
    base = input("Which base? (2-36, 10 for decimal) \n> ")
    digits = input("How many digits? (enter a big number, say, 10000)\n> ")
    tofile = raw_input("Output to file? (enter a filename, or just press " \
        "enter\nto print directly to the screen) \n> ")
    if tofile:
        tofile = open(tofile, "w")

    calculateit(base, digits, tofile)
    raw_input("\nPress enter to close this script.")

if __name__ == "__main__":
    interactive()