New submission from Akima:
1 / 0 (where both numbers are decimal.Decimal) produces a
decimal.DivisionByZero exception as I would expect. This is useful. I can use
a simple try except block to catch a potential division by zero error in my
code.
0 / 0 (where both numbers are decimal.Decimal) produces a
decimal.InvalidOperation exception. This is undesirable. I would expect
another decimal.DivisionByZero exception. This means that if I want to catch a
division by zero error in my code using a try except block, I now have to catch
exceptions for both decimal.DivisionByZero and decimal.InvalidOperation.
Presumably decimal.InvalidOperation can be raised in other scenarios, so
catching it may result in masking a programming fault (which isn't just a
division by zero: 0 / 0).
If you perform the same division but using standard Python integers instead of
decimal.Decimal objects, the behaviour is exactly as you would expect: 0 / 0
and 1 / 0 both produce a ZeroDivisionError exception.
I have tested this in CPython 3.3.5, 3.2.3 and 2.7.3. All versions produce the
same behaviour.
Demonstration:
Python 2.7.3 (default, Feb 27 2014, 19:58:35)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from decimal import Decimal as d
>>> d(1) / d(0)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/decimal.py", line 1323, in __truediv__
return context._raise_error(DivisionByZero, 'x / 0', sign)
File "/usr/lib/python2.7/decimal.py", line 3866, in _raise_error
raise error(explanation)
decimal.DivisionByZero: x / 0
>>> d(0) / d(0)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/decimal.py", line 1322, in __truediv__
return context._raise_error(DivisionUndefined, '0 / 0')
File "/usr/lib/python2.7/decimal.py", line 3866, in _raise_error
raise error(explanation)
decimal.InvalidOperation: 0 / 0
>>> 1 / 0
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ZeroDivisionError: integer division or modulo by zero
>>> 0 / 0
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ZeroDivisionError: integer division or modulo by zero
>>>
Here is the same demonstration but using a Python 3.2.3 interpreter:
Python 3.2.3 (default, Feb 27 2014, 21:31:18)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from decimal import Decimal as d
>>> d(1) / d(0)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.2/decimal.py", line 1300, in __truediv__
return context._raise_error(DivisionByZero, 'x / 0', sign)
File "/usr/lib/python3.2/decimal.py", line 3926, in _raise_error
raise error(explanation)
decimal.DivisionByZero: x / 0
>>> d(0) / d(0)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.2/decimal.py", line 1299, in __truediv__
return context._raise_error(DivisionUndefined, '0 / 0')
File "/usr/lib/python3.2/decimal.py", line 3926, in _raise_error
raise error(explanation)
decimal.InvalidOperation: 0 / 0
>>> 1 / 0
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ZeroDivisionError: division by zero
>>> 0 / 0
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ZeroDivisionError: division by zero
>>>
----------
messages: 226125
nosy: akima
priority: normal
severity: normal
status: open
title: Inconsistent division by 0 behaviour in decimal module
type: behavior
versions: Python 2.7, Python 3.2, Python 3.3
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Python tracker <[email protected]>
<http://bugs.python.org/issue22306>
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