What's a literal? The only other time I heard about it was studying
I don't know what literal is. So, it won't help me to understand ellipsis,
I really thought it was that oval shaped figure.
Wiki says: "Literals are often used to initialize variables"
I suppose it's just a place holder, though I don't know when I would use it
in my every day life.
On Thu, Aug 10, 2017 at 8:47 AM, Steven D'Aprano <st...@pearwood.info>
> On Wed, Aug 09, 2017 at 12:06:37PM -0400, C W wrote:
> > Dear Python experts,
> > What exactly does the three dots do?
> > > aList = ...
> ... is literal syntax for the Ellipsis singleton object.
> Ellipsis was added to the language at the express request of the numpy
> developers. Although numpy is a third-party project outside of the
> standard library, it is big enough and important enough that their
> requests carry a LOT of weight with the core Python devs. Other features
> Python has that were originally added at the request of numpy include:
> - extended slicing with two colons obj[a:b:c]
> - the @ operator used by numpy for matrix multiplication.
> I don't know what Ellipsis is used for by numpy, but now it makes a
> convenient pseudo-pass command:
> class X:
> def func():
> > It's an ellipsis, a spot holder to later. But what data type is it:
> > matrix?
> Its a singleton object. Think of it as a sibling to None and
> NotImplemented, but with optional funny syntactic sugar ... to refer to
> None is a special value used as "no such value", or nil or null;
> NotImplemented is a special value used by operator dunder methods like
> __add__ and __mul__ to mean "I can't handle this argument";
> Ellipsis is a special value used by numpy to mean whatever it is that
> numpy uses it to me.
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