On Tue, 09 Oct 2012 02:00:04 +1100, Chris Angelico wrote: > On Tue, Oct 9, 2012 at 1:48 AM, Dave Angel <d...@davea.name> wrote: >> import decimal >> a = decimal.Decimal(4.3) >> print(a) >> >> 5.0999999999999996447286321199499070644378662109375 > > Ah, the delights of copy-paste :) > >> The Decimal class has the disadvantage that it's tons slower on any >> modern machine I know of... > > Isn't it true, though, that Python 3.3 has a completely new > implementation of decimal that largely removes this disadvantage?
Yes. It's blazingly fast: up to 120 times faster than the pure Python version, and within an order of magnitude of the speed of binary floats: [steve@ando ~]$ python3.3 -m timeit -s "x, y = 1001.0, 978.0" > "x+y-(x/y)**4" 1000000 loops, best of 3: 0.509 usec per loop [steve@ando ~]$ python3.3 -m timeit -s "from decimal import Decimal" > -s "x, y = Decimal(1001), Decimal(978)" "x+y-(x/y)**4" 100000 loops, best of 3: 3.58 usec per loop Without hardware support, Decimal will probably never be quite as fast as binary floats, but its fast enough for all but the most demanding needs. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
