2018-04-24 18:31 GMT+03:00 Chris Angelico <rosuav@gmail.com>:

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