[Python-Dev] == on object tests identity in 3.x (original) (raw)

Ethan Furman ethan at stoneleaf.us
Tue Jul 8 05:47:23 CEST 2014

On 07/07/2014 08:34 PM, Stephen J. Turnbull wrote:

Ethan Furman writes:

And what would be this 'sensible definition' [of value equality]? I think that's the wrong question. I suppose Andreas's point is that when the programmer doesn't provide a definition, there is no such thing as a "sensible definition" to default to. I disagree, but given that as the point of discussion, asking what the definition is, is moot.

He eventually made that point, but until he did I thought he meant that there was such a sensible default definition, he just wasn't sharing what he thought it might be with us.

2) The 'is' operator is specialized, and should only rarely be needed. Nitpick: Except that it's the preferred way to express identity with singletons, AFAIK. ("if x is None: ...", not "if x == None: ...".)

Not a nit at all, at least in my code -- the number of times I use '==' far outweighs the number of times I use 'is'. Thus, 'is' is rare.

(Now, of course, I'll have to go measure that assertion and probably find out I am wrong :/ ).

-- Ethan

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