[Pypgsql-devel] [ pypgsql-Bugs-1755777 ] PgNumeric += is strange

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Bugs item #1755777, was opened at 2007-07-17 18:56
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Category: PgNumeric
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Ken Lalonde (kenlalonde)
Assigned to: Nobody/Anonymous (nobody)
Summary: PgNumeric += is strange

Initial Comment:
The augmented arithmetic operations on PgNumeric instances will update the object directly,
instead of creating a new one.
This leads to unexpected results such as:

   $ cat t.py
   from pyPgSQL.PgSQL import PgNumeric
   a = PgNumeric(1.0)
   b = a
   b += 1
   print a, b
   $ python t.py
   2.0 2.0

Here we see b is incremented, but both a and b
are changed, because the __iadd__ method updates
b in place.

Call me naive, but I would expect "b += 1"
to behave exactly like "b = b+1".

Perhaps PgNumeric should allocate a new object
if the old one has multiple references?
I'm not sure, but the current behavior
is not intuitive, and leads to hard-to-find bugs.



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