On Thu, Apr 26, 2018 at 4:27 PM, Kirill Balunov <kirillbalu...@gmail.com> wrote:
>
>
> 2018-04-24 18:31 GMT+03:00 Chris Angelico <ros...@gmail.com>:
>>
>>
>>
>
> Not sure, but if additional motivating examples are required, there is a
> common pattern for dynamic attribute lookup (snippet from `copy.py`):
>
> reductor = dispatch_table.get(cls)
> if reductor:
> rv = reductor(x)
> else:
> reductor = getattr(x, "__reduce_ex__", None)
> if reductor:
> rv = reductor(4)
> else:
> reductor = getattr(x, "__reduce__", None)
> if reductor:
> rv = reductor()
> else:
> raise Error("un(shallow)copyable object of type %s" % cls)
>
> which can with the current `binding expression` syntax simplified to:
>
> if reductor := dispatch_table.get(cls):
> rv = reductor(x)
> elif reductor := getattr(x, "__reduce_ex__", None):
> rv = reductor(4)
> elif reductor := getattr(x, "__reduce__", None):
> rv = reductor()
> else:
> raise Error("un(shallow)copyable object of type %s" % cls)
>
To me this looks more like a motivating example for adding
GOTO statement to Python... Anybody writing a PEP? :)
And should not the above be wrapped in a function?
(a workaround in abscence of GOTO)
Also, the ELIF is merely an edge case: once you
have something like:
if value :
rv = f(x)
else :
temp = ...
value = f1(temp)
print (value)
if value :
rv = f2(x)
...
then it does not wrap into anything anymore.
Mikhail
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