On 08/18/2014 03:04 PM, Chris Kaynor wrote:
On Mon, Aug 18, 2014 at 2:42 PM, Ethan Furman wrote:
If you are not dealing with singletons (which is most cases), such as numbers,
strings, lists, and most other
arbitrary objects, you will need to use "!=" or anytime the two objects you are
comparing are not the exact same
object, you can easily get the wrong answer.
For example, in CPython 3.4.1:
(254 + 3) is 257
False
(254 + 3) == 257
True
('asd' + '@sd') is 'asd@sd'
False
('asd' + '@sd') == 'asd@sd'
True
However, when testing these cases, you need to be careful due to optimizations
like smaller integer interning and string
interning:
(254 + 2) == 256
True
(254 + 2) is 256
True
('asd' + 'sd') == 'asdsd'
True
('asd' + 'sd') is 'asdsd'
True
In each of these cases, the behavior may be different in other implementations
or versions of Python.
But the point to remember is that, for equal objects, '==' will work, 'is' may
or may not.
--
~Ethan~
--
https://mail.python.org/mailman/listinfo/python-list
