[Python-Dev] Let's just keep lambda (original) (raw)

Brett Cannon brett at python.org
Tue Feb 7 22:52:51 CET 2006

On 2/7/06, Paul Moore <p.f.moore at gmail.com> wrote:

On 2/7/06, Brett Cannon <brett at python.org> wrote: > On 2/5/06, Guido van Rossum <guido at python.org> wrote: > > After so many attempts to come up with an alternative for lambda, > > perhaps we should admit defeat. I've not had the time to follow the > > most recent rounds, but I propose that we keep lambda, so as to stop > > wasting everybody's talent and time on an impossible quest. > > I have been thinking about this, and I have to say I am a little > disappointed (-0 disappointed, not -1 disappointed). I honestly > bought the argument for removing lambda. And I think that a deferred > object would help with one of lambda's biggest uses and made its loss > totally reasonable.

I'm not 100% sure what you mean here, but as far as my understanding goes, current lambda is a "deferred object" (or at least a "deferred expression", which may not be quite what you mean...)

Yes, lambda is deferred. What I mean is using lambda for things like lambda x: x.attr and such; specifically for deferred execution, and not for stuff like lambda x: func(1, 2, x, 3, 4) stuff.

> But I know that everyone and their email client is against me on this > one, so I am not going to really try to tear into this. But I do > think that lambda needs a renaming.

I agree with this. The name "lambda" is a wart, even if the deferred expression feature isn't. My preference is to simply replace the keyword lambda with a keyword "expr" (or if that's not acceptable because there's too much prior use of expr as a variable name, then maybe "expression" - but that's starting to get a bit long). > Speaking as someone who still > forgets that Python's lambda is not the same as those found in > functional languages, Well, only in the sense that Python's expressions are not the same as those found in functional languages (ie, Python has statements which are not expressions). But I see your point - and I strongly object to going the other way and extending lambda/expr to allow statements or suites. > I would much rather have it named 'expr' or > 'expression' or something that is more inline with its abilities then > with a name taken for CS historical reasons. This ain't for father's > lambda and thus shouldn't be named so. Agreed. But if "expr" isn't acceptable, I don't like the other common suggestion of reusing "def". It's not a definition, nor is it "like an anonymous function" (the lack of support for statements/suites being the key difference).

Yeah, reusing def is taking back into the functional world too much. It makes our current use of def seem more like syntactic sugar for assigning a lambda to a name for function definition and that is not what is happening here.

> Then again, Guido did say he "should", not that he "did" admit defeat. =)

OTOH, he was trying to stop endless the discussion... :-)

=) Well, it should when Python 3 comes out, so there is some extra incentive for that to happen sooner than later.

-Brett

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