On Mon, Jul 23, 2018 at 8:08 AM Grégory Lielens
<gregory.liel...@gmail.com> wrote:
>
>
>
> On Monday, July 23, 2018 at 8:24:45 AM UTC+2, Nicholas Cole wrote:
>
>> And that leads to a simple question: how many times does this actually
>> occur in real-world by python code? -- i.e. how many times do I want
>> to check the value of an existing label, and, finding it is None (and
>> None specifically), then assign it a value?
>
>
> The PEP present a few examples.
>
> I think the compactness and clarity is really gained when doing a descent
> into an "attribute tree", where any (or selected) members can be None, like
> getting back to the example by Steven (spell-corrected, and expanded):
>
> meal = obj?.spam?.eggs.tomato?.cheese ?? "Mozzarella"
>
> Where, to put the proposal in even better light, I have assumed that eggs
> instances always have a tomato attributes (i.e. are never None).
>
> This is indeed much more compact that the current version, and arguably more
> readable (it's easier to parse once you know the syntax...but you have to
> know the special syntax that will be used for this kind of stuff only). The
> more you deepen the attribute access, the more you gain, but of course deep
> attribute access is not so common. The new operators may make deep attribute
> hierarchies (or deeply nested dicts/lists) slightly more common, and there
> also I do not think it's a good thing.
>
That above example looks terrible to read (to me). Yes, that's a
subjective statement. This example from the PEP is even worse:
Example:
if entry.is_dir():
dirs.append(name)
if entries is not None:
entries.append(entry)
else:
nondirs.append(name)
After updating to use the ?. operator:
if entry.is_dir():
dirs.append(name)
entries?.append(entry)
else:
nondirs.append(name)
In the first, it's totally clear to me when entries would be appended
to and when it wouldn't. The second I had to read several times
before I could see what was going on. The fact that it is already
embedded in an if...else statement perhaps made it harder to
understand.
I guess people will say that we will just get used to the new syntax,
but I don't see the benefit of making that particular "if" statement
more compact, and leaving all the others in place. Or to put it
another way, I'm just not convinced that "None" is sufficiently
special.
N.
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