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.

Basically it's about adding := as an "assignment expression operator", that does assignment and returns the value as an expression. That is, take this regex example:

    match1 = re1.match(text)

    if match1 is not None:
        do_stuff()
    else:
        match2 = re2.match(text)

        if match2 is not None:
            do_other_stuff()

Which is a bit clunky. you only want to evaluate match2 in case match1 fails, but that means a new level of nesting. Instead, with this proposal, you could do this:

    if (match1 := re1.match(text)) is not None:
        do_stuff();
    elif (match2 := re2.match(text)) is not None:
        do_other_stuff()

Evaluate and assign in the if-statement itself. This is not dissimilar to the equals operator in C. In C, you would frequently find loops like `while ((c = read()) != EOF) { ... }`. This would presumably allow a similar pattern in python as well.

More information can be found in PEP-572: https://www.python.org/dev/peps/pep-0572/

Hehe. More chances for C-style bugs like:

if (a = b) /* Oooops, meant a == b! */