[Python-Dev] (name := expression) doesn't fit the narrative of PEP 20

[David Mertz]

>
> [Raymond Hettinger <raymond.hettinger at gmail.com>]
> > Python is special, in part, because it is not one of those languages.
> > It has virtues that make it suitable even for elementary school children.
> > We can show well-written Python code to non-computer folks and walk
> > them through what it does without their brains melting (something I can't
> > do with many of the other languages I've used).  There is a virtue
> > in encouraging simple statements that read like English sentences
> > organized into English-like paragraphs, presenting itself like
> > "executable pseudocode".


While this is true and good for most Python code, can you honestly explain
asyncio code with async/await to these non-programmers?! What about the
interfaces between async and synchronous portions?

I've been programming for 40 years, in Python for 20 of them. I cannot read
any block of async code without thinking VERY SLOWLY about what's going on,
then getting it wrong half the time. I even teach Python almost as much as
Raymond does.

There's a certain hand-waving approach to teaching async/await where you
say not to worry about those keywords, and just assume the blocks are
coordinated "somehow, behind the scenes." That's not awful for reading
*working* code, but doesn't let you write it.

I'm not saying binding expressions are likewise reserved for a special but
important style of programming. If included, I expect them to occur
more-or-less anywhere. So Raymond's concern about teachability is more
pressing (I've only taught async twice, and I know Raymond's standard
course doesn't do it, all the other code is unaffected by that unused
'await' lurking in the syntax). Still, there are good reasons why not all
Python code is aimed at non-computer folks.
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