2018年04月24日 18:31 GMT+03:00 Chris Angelico <[email protected]>:
>
> Recommended use-cases
> =====================
>
> [...]
>
> # Capturing regular expression match objects
> # See, for instance, Lib/pydoc.py, which uses a multiline spelling
> # of this effect
> if match := re.search(pat, text):
> print("Found:", match.group(0))
>
>
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)
which becomes much clearer, at least in my opinion.
With kind regards,
-gdg
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