What if we used ? after the statement beginning?
name ?= person.name
custom_query ?= entity.get_query(context)
# Becomes None if entity is None. Raise an exception if entity is not None and
get_query is None or undefined.
custom_query ??= entity.get_query(context)
# If entity, entity.get_query, entity.get_query(context) evaluate to null, the
operation short-circuits and custom_query becomes None
await? foo
with? bar as baz:
# this only runs if bar is not None
pass
?= only short circuits into None when the first evaluation is None (the weak
operator)
??= short circuits into None whenever any evaluation is None or raises an
AttributeError. (the strong operator)
I’m imagining the strong operator would be useful especially for duck typing.
No more hasattr checks, no more isinstance checks.
I would like to see some real world use cases for none aware operators that
couldn’t be covered by these none aware assignment operators.
Previous code:
# original code
a ?= b.c
# another, second, programmer comes along and changes it to
a ?= b.c.d
The interpreter would raise an exception, if “d” was None or not defined on
“c”. If this is intended behavior, this forces the second programmer to
explicitly mark that all attribute access is coalescing with the strong
operator, instead of the interpreter swallowing the exception now and emitting
an exception later. The previous code assumes “b” is None, which in reality may
represent the state of a network socket or a file transfer. The program may
display that the operation was complete, leading to a bug in the output.
I believe this is more readable as well.
> On Jul 25, 2018, at 7:32 PM, [email protected] wrote:
>
> PEP 505: None-aware operators
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