[Python-ideas] Fwd: Null coalescing operator

[David Mertz]

On Sun, Sep 11, 2016 at 6:11 PM, Guido van Rossum <guido at python.org> wrote:

> On Sun, Sep 11, 2016 at 6:00 PM, David Mertz <mertz at gnosis.cx> wrote:
> >     None if a is None else a.foo
>
> This is the crux of the matter to me. It's just too verbose, and the
> `if` and `else` keywords are lost in the noise of all the other words
> on the line. Plus the big win when it applies) is that if `a` is in
> fact something more complex, like `f(a)`, repeating it twice sounds
> like a performance penalty, and that's where `f(a)?.foo` really
> shines.
>

The non-repetition is certain a plus, I readily confess.  It's not only
performance even; `f()` might not be a pure function. Silly example:

>>> def f(a):
....     if random() < .01:
....         return None
....     class V: pass
....     v = V()
....     v.foo = random()*a
....     return v



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