Comments on: You know you need to install a new Python version when…

By: lorg

lorg — Tue, 17 Mar 2009 19:13:07 +0000

It seems Issue 2531 references this bug. I don't think it should have been rejected, as this behavior is problematic, and was also "declared incorrect" in Python 3.

By: Chris

Chris — Wed, 11 Mar 2009 12:59:32 +0000

Small typo in the above:

float(decimal.Decimal(’0.2′) < 0.3)

Should be:

float(decimal.Decimal(’0.2′)) < 0.3

By: Chris

Chris — Wed, 11 Mar 2009 12:57:21 +0000

This is indeed a pain. The fix is to do:

float(decimal.Decimal(’0.2′) < 0.3)

Obviously this isn’t ideal though. The reasons for this are down to the differences precision in floats and decimals. There’s an explanation for it in this patch for python 3000:

http://mail.python.org/pipermail/python-3000-checkins/2008-November/004843.html

“Comparison of objects of the differing types depends on whether either
of the types provide explicit support for the comparison. Most numberic types
can be compared with one another, but comparisons of :class:`float` and
:class:`Decimal` are not supported to avoid the inevitable confusion arising
from representation issues such as “float(’1.1′)“ being inexactly represented
and therefore not exactly equal to “Decimal(’1.1′)“ which is. When
cross-type comparison is not supported, the comparison method returns
“NotImplemented“. This can create the illusion of non-transitivity between
supported cross-type comparisons and unsupported comparisons. For example,
“Decimal(2) == 2“ and `2 == float(2)“ but “Decimal(2) != float(2)“.”

By: Arkon

Arkon — Wed, 11 Mar 2009 12:48:37 +0000

It doesn’t have anything todo with that issue.
I am really dumbstruck how they released a module with such bugs.
I suggest you to install python on a clean machine and check it out again.