decimal_rounding.py

#!/usr/bin/env python


import decimal

context = decimal.getcontext()

ROUNDING_MODES = [
    'ROUND_CEILING',
    'ROUND_DOWN',
    'ROUND_FLOOR',
    'ROUND_HALF_DOWN',
    'ROUND_HALF_EVEN',
    'ROUND_HALF_UP',
    'ROUND_UP',
    'ROUND_05UP',
]
header_fmt = '{:10} ' + ' '.join(['{:^8}'] * 6)

print header_fmt.format(' ',
                        '1/8 (1)', '-1/8 (1)',
                        '1/8 (2)', '-1/8 (2)',
                        '1/8 (3)', '-1/8 (3)',
                        )

for rounding_mode in ROUNDING_MODES:
    print '{0:10}'.format(rounding_mode.partition('_')[-1]),
    for precision in [1, 2, 3]:
        context.prec = precision
        context.rounding = getattr(decimal, rounding_mode)
        value = decimal.Decimal(1) / decimal.Decimal(8)
        print '{0:^8}'.format(value),
        value = decimal.Decimal(-1) / decimal.Decimal(8)
        print '{0:^8}'.format(value),
    print