[ python-Bugs-1355842 ] Incorrect Decimal-float behavior for += and *=

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Bugs item #1355842, was opened at 2005-11-13 11:17
Message generated for change (Comment added) made by connelly
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Category: Python Library
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Connelly (connelly)
Assigned to: Nobody/Anonymous (nobody)
Summary: Incorrect Decimal-float behavior for += and *=

Initial Comment:
The += and *= operators have strange behavior when the
LHS is a Decimal and the RHS is a float (as of
2005-11-13 CVS decimal.py).

Example:

>>> d = Decimal('1.02')
>>> d += 2.1
>>> d
NotImplemented

A blatant violation of "Errors should never pass silently."

Also, a bad error description is produced for the *=
operator:

>>> d = Decimal('1.02')
>>> d *= 2.9
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: can't multiply sequence by non-int


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>Comment By: Connelly (connelly)
Date: 2005-12-02 06:17

Message:
Logged In: YES 
user_id=1039782

The += and *= operations also give the same strange behavior
when the LHS is a Decimal and the RHS is str or unicode:

>>> d = Decimal("1.0")
>>> d += "5"
>>> d
NotImplemented

>>> d = Decimal("1.0")
>>> d *= "1.0"
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: can't multiply sequence by non-int


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Comment By: Neal Norwitz (nnorwitz)
Date: 2005-11-14 04:43

Message:
Logged In: YES 
user_id=33168

Hmmm.  __add__ returns NotImplemented which works with
classic classes, but not new-style classes.  I wonder if
NotImplementedError is supposed to be raised for new-style
classes.  

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