!!!Python Decimal
[Python]
[Python Osmosis|http://python.secsup.org/?p=138]

!!Decimal
*from decimal で利用
*小数点以下の計算も正しく行う
*getcontext().prec で有効桁数を設定

 Python 2.6.3 (r263rc1:75186, Oct  2 2009, 20:40:30) [MSC v.1500 32 bit (Intel)] on win32
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 >>> from decimal import *
 >>> Decimal('0.70') * Decimal('1.05')
 Decimal('0.7350')
 >>> .70 * 1.05
 0.73499999999999999
 >>> Decimal('1.00') % Decimal('.10')
 Decimal('0.00')
 >>> 1.00 % 0.10
 0.09999999999999995
 >>> sum([Decimal('0.1')] * 10) == Decimal('1.0')
 True
 >>> sum([0.1] * 10) == 1.0
 False
 >>> getcontext().prec = 36
 >>> Decimal(1) / Decimal(7)
 Decimal('0.142857142857142857142857142857142857')