Given the arguments you've raised, I am now inclined to agree with you.
However, for completeness of the discussion, I want to indicate the primary
intended use case:
def fn(x=None):
if not x:
x = some_complex_or_runtime_dependent_result()
For me this appears quite frequently. Admittedly the condition should
likely be `x is None`.
On 26 March 2018 at 14:41, Steven D'Aprano <st...@pearwood.info> wrote:
> On Mon, Mar 26, 2018 at 01:48:34PM +0100, Cammil Taank wrote:
> > Hi,
> >
> > I find a common idiom in Python is:
> >
> > x = x or 'some other value'
>
> I don't find it very common. I don't think I've ever used it or seen it.
> I've occasionally used:
>
> spam = eggs or 'something'
>
> but mostly I use:
>
> result = function(eggs or 'something')
>
> (and even that is quite unusual). But others may use it more often.
>
>
> > This is highly reminiscent of the problem inplace operators solve.
>
> Not really: the other augmented operators all connect to ordinary
> operators that can be overloaded. But `or` is special, it's a
> short-cutting operator that is treated specially by the interpreter.
>
> And even if x is mutable, there's no way to make this an in-place
> operation. After `x = x or y`, there are only two possibilities:
>
> - x is still a reference to whatever it was before the operation;
> - or x now refers to the same object as y.
>
> So this is very different behaviour to (say) += and the other augmented
> operators.
>
>
> > Would it be a good idea to consider an inplace operator for this,
> perhaps:
> >
> > x or= 'some other value'
>
> Mixing a keyword with a symbol like that looks really weird.
>
> Others may disagree, but to me, this pattern isn't common enough to
> justify specialist syntax. I might be a little less negative if the
> syntax didn't look so strange to me.
>
> But only a little.
>
>
> --
> Steve
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