Mark Dickinson <dicki...@gmail.com> added the comment:

Float-to-decimal comparisons have been fixed, and the Decimal hash function 
changed so that numerically equal Decimal and float instances hash equal, in 
r79583.

The idea of raising an exception for float<->Decimal comparisons was discarded 
partly for backwards compatibility reasons, and partly because having __eq__ 
raise an exception causes difficulties for sets and dicts:  for example, if 
equality checks between floats and Decimals raised an exception then '{-1.0, 
Decimal(-3)}' would give a valid set (the two values have different hashes, so 
the Decimal.__eq__ method is never invoked), but '{-1.0, Decimal(-2)}' would 
raise an exception (because the two set elements have equal hashes, so 
Decimal.__eq__ is invoked in order to determine whether the two elements are 
equal or not).

(General principle:  if x and y are hashable, x == y should never raise an 
exception.)

This is still only a partial fix:  comparisons between Decimal and Fraction 
instances still behave oddly.  This seems less likely to cause problems in 
real-life code, though.  The changes needed to make Decimal <-> Fraction 
comparisons correct are too intrusive and not yet well tested enough to make it 
into 2.7.  (See issue 8188).

As discussed on python-dev, I'll forward port this to py3k;  with any luck, 
py3k will also grow valid comparisons for Decimal <-> Fraction.

----------
versions:  -Python 2.7

_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue2531>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

Reply via email to