PEP 572: Python assignment expressions has been accepted

What is it? The link points to a discussion more deep than I’m willing to read.

It's a controversial PEP https://www.python.org/dev/peps/pep-0572/ which allows you to write Python like this:

    def foo():
        if n := randint(0, 3):
            return n ** 2
        return 1337


    [(x, y, x/y) for x in input_data if (y := f(x)) > 0]

This immediately looks useful for things like:

    if foo := bar[baz]:
        bar[baz] += 1
        return foo
    else:
        bar[baz] = 1
        return 0

Where foo is a dict keeping track of multiple things, and a non-existing key (baz) is never an error but rather the start of a new count. Faster and more readable than

    if baz in list(bar.keys()):
    ....

Similar to Swift’s ‘if let’, it seems.