"/a" is not "/a" ?

[Mel]

Emanuele D'Arrigo wrote:
> Gary, thanks for your reply: your explanation does pretty much answer
> my question. One thing I can add however is that it really seems that
> non-alphanumeric characters such as the forward slash make the
> difference, not just the number of characters. I.e.

(Actually, we had this thread last week.)  It's a question of strings that 
might be Python names.  Every line of code that looks up a name in a 
namespace (e.g. global symbols, instance attributes, class attributes, etc.) 
needs a string containing the name.  This optimization keeps Python data 
space from filling up with names.  The same thing happens with small, 
common, integers.
[ ... ]
> I just find it peculiar more than a nuisance, but I'll go to the
> blackboard and write 100 times "never compare the identities of two
> immutables". Thank you all!

The rule is to know the operations, and use the ones that do what you want 
to do.  `is` and `==` don't do the same thing.  Never did, never will.

<sarcasm>
Python 2.5.2 (r252:60911, Oct  5 2008, 19:24:49)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> a=3
>>> b=0
>>> a+b == a-b
True
>>> b=1
>>> a+b == a-b
False

At this point, someone says 'Eek'.  But why?  `+` and `-` never were the 
same operation, regardless of a coincidence or two.
</sarcasm>

	Mel.