Why prefer != over <> for Python 3.0?

[Steven D'Aprano]

On Sat, 29 Mar 2008 04:08:16 -0700, Paul Rubin wrote:

> kwitters at telenet.be writes:
>> I don't know if this is the right place to discuss the death of <> in
>> Python 3.0, or if there have been any meaningful discussions posted
>> before (hard to search google with '<>' keyword), but why would anyone
>> prefer the comparison operator != over <>???
> 
> I doubt anyone cares.  

[channeling Luke Skywalker sotto voice]
I care.


> Python probably chose != because it's what C uses.

Coming from a background in Pascal, I originally hated the look of != and 
preferred <> but I've now got used to the look of it.

When I design my own language (ha!), I'll use != for "not equal to" and 
reserve <> for "greater than or less than but not equal to" which is 
subtly different. (Think about unordered values, where x != y does not 
imply that x < y or x > y, e.g. IEEE NaNs.)

> The scary choice is /= which can be interpreted as an assignment. 

"Can be"?

>>> x = 5.0
>>> x /= 2
>>> x
2.5


Koen, I've read your blog and I'm afraid that your reasoning is specious. 
You say:

[quote]
For comparison (not assignment!), they use operators like <, >, <= 
(smaller or equals), >= (larger or equals), == (double '=' so there is no 
confusion with assignment).

All pretty clear hey? But now comes the catch, there exists an operator 
!=... but what does it mean? Well, that one is pretty easy, of course ! 
must be an operator of its own (in non-python languages meaning 'not'), 
and it resembles the fancy assignment statement, so 
        a != b

must mean "assign the value 'not b' to 'a'... right?... Wrong! Somehow 
this is a comparison operator meaning "not equals"... what??? Yes, that's 
right, but hey, you learn to live with it eventually.
[end quote]

Given that <= is a comparison operator, not an assignment, why do you 
jump to the conclusion that != is an assignment? Why don't you argue that 
"x <= y" means "assign the value of x<y to x"?

Since you jump to an invalid conclusion about !=, the rest of your 
argument fails.



-- 
Steven