Significant figures in the decimal module

Posted by Jason Baker on Stack Overflow See other posts from Stack Overflow or by Jason Baker
Published on 2008-09-27T18:47:54Z Indexed on 2010/04/15 20:13 UTC
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So I've decided to try to solve my physics homework by writing some python scripts to solve problems for me. One problem that I'm running into is that significant figures don't always seem to come out properly. For example this handles significant figures properly:

from decimal import Decimal
>>> Decimal('1.0') + Decimal('2.0')
Decimal("3.0")

But this doesn't:

>>> Decimal('1.00') / Decimal('3.00')
Decimal("0.3333333333333333333333333333")

So two questions:

  1. Am I right that this isn't the expected amount of significant digits, or do I need to brush up on significant digit math?
  2. Is there any way to do this without having to set the decimal precision manually? Granted, I'm sure I can use numpy to do this, but I just want to know if there's a way to do this with the decimal module out of curiosity.

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