[Python-ideas] PEP 505: None-aware operators

[David Mertz]

On Tue, Jul 24, 2018, 9:09 AM Chris Angelico <rosuav at gmail.com> wrote:

> >>> x = Foo(cfg).user.profile
> >>> x.food
>
> Remember, these lines could be a very long way apart. You could pass
> 'x' to a function unrelated to the line of code that created it. And
> 'x.food' still has to have the magic. You can't mandate that the call
> to Coalesce be on the same line as the attribute access - Python
> doesn't work that way.
>
> So your perfectly ordinary dot operator now does magic in addition to
> normal attribute access. See why it's a dangerous thing?
>

Yes, of course. That's why I would recommend best practice is to unbox or
otherwise use the conditional value as close to the magic code as feasible.

Likewise, as I noted a little while ago, 'x.food' could equally well be a
property that executed arbitrarily slow, magical, obscure, or even
malicious operations. Equally, 'x + y' could do absolutely anything if we
define .__add__() or .__radd__() methods.

Everything in Python is magical in that sense, but we should deliberately
keep the magic constrained to the amount needed.

>
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