On 2016-09-12 01:26, Guido van Rossum wrote:
On Sun, Sep 11, 2016 at 12:44 PM, Daniel Moisset
<dmois...@machinalis.com> wrote:
Both this discussion, PEP 505, and the one a year ago, tend to mix up 2
related but separate proposals:
I don't think there's that much of a mix-up. PEP 505 clearly describes
each proposal separately and even gives a choice to accept or reject
each one separately.
(A) Add a None-coalescing operator (like C# a ?? b, what you would write in
Python as "a or b" if it didn't have the falsy gotcha)
https://www.python.org/dev/peps/pep-0505/#none-coalescing-operator
(B) Add some None-aware navigation operators ( The "?.", "?()", "?[]", or
what you would write in python as "a and a.attribute" if it didn't have the
falsy gotcha)
https://www.python.org/dev/peps/pep-0505/#none-aware-attribute-access-operator
Both are things that can be already done in python, so the purpose here is
to add some convenience (aka "syntax sugar"). IMO, this kind of syntax sugar
proposals should be weighed with the frequency of the coding pattern where
the sugar can be applied. And from the stats presented in PEP-505 (B) is one
order of magnitude less usual than (A); that matches most of the examples I
see in the threads and FWIW my personal experience.
I can't argue here yet. Honestly I looked at some examples; for those
where it wasn't instantly clear that a None-coalescing operator would
*not* help, I found it hard to figure out how to rewrite it. E.g. this
one -- quick, is there a better way?
return "Illegal Argument" + (self.message is not None and (": " +
self.message) or "")
I think this is better:
return "Illegal Argument" + ("" if self.message is None else ": " +
self.message)
but it doesn't require a None-coalescing operator.
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