# -*- coding: utf-8 -*-
# http://fr.wikipedia.org/wiki/Pr%C3%A9fixe_du_syst%C3%A8me_international
import sys, locale

encoding = sys.stdout.encoding or locale.getpreferredencoding()

numbers = [1.236, 1742, 0.5698, 4569874, 356, 0.000698]

def printWithUnit(number):
    units = [(u'G', 1e9),
             (u'M', 1e6),
             (u'K', 1e3),
             (u' ', 1.0),
             (u'm', 1e-3),
             (u'µ', 1e-6),
             (u'n', 1e-9)]
    for unit, coeff in units:
        if number > coeff:
            return u"%5.1f %s" % (number / coeff, unit)
    return u"%.1g" % number

for number in numbers:
    print(printWithUnit(number).encode(encoding))