[Python-Dev] Type hints -- a mediocre programmer's reaction

[Chris Barker]

Thank you Jack.

Jack: "I hate code and I want as little of it as possible in our product"

I love that quote -- and I ALWAYS use it when I teach newbies Python. It's
kind of the point of Python -- you can get a lot done by writing very
little code.

I'm still confused about what all this type annotation is about -- yes, I
certainly see lots of advantages to static typing -- but also many
disadvantages. And one of them is a bunch more stuff to read and write.

But key is: If you like typing, use a statically typed language.

If you want the advantages of dynamic typing -- then why do you want all
the extra clutter and "safety"?

And it seems to me that optional/partial typing buys you much of the hassle
and restrictions, and essentially NONE of the safety (type casting pointers
in C, anyone?).

And I've had this debate with proponents of JAVA and the like a bunch --
sure, type checking will catch bugs in your code -- but they are almost
always shallow bugs -- and bugs that if your tests didn't catch them, you
have really lame tests!

On the other had, you just can't get good performance doing low-level
things with a dynamic language. So I use Cython, which, in a way, is Python
with optional static typing.  It gives you down to the metal performance,
where, and only where, you need it, but not really much in the way of type
checking.

However, this is exactly the opposite of what everyone seem to be talking
about using optional typing in Python for -- which is type checking ,but
not any run-time optimizations -- in fact, AFAICT, not even run-time type
checking.

So a whole lot of clutter for very little gain. :-(

NOTE: MyPy is out in the wild -- I'd be really interested to see how it all
is really working out -- even on those "enterprise" code bases -- other
than managers feeling better, are developers finding out that:

"WOW -- this baby caught some nasty, bugs that I would not have found with
testing -- and would have been hard to debug after the fact!"

But in the end, I agree with the OP here -- stub files let pre-run-time
static type checking happen without cluttering up Python for the rest of us
-- so a nice compromise.

So I guess we'll see.

- Chris

On Mon, Apr 20, 2015 at 4:41 PM, Jack Diederich <jackdied at gmail.com> wrote:

> Twelve years ago a wise man said to me "I suggest that you also propose a
> new name for the resulting language"
>
> I talked with many of you at PyCon about the costs of PEP 484. There are
> plenty of people who have done a fine job promoting the benefits.
>
> * It is not optional. Please stop saying that. The people promoting it
> would prefer that everyone use it. If it is approved it will be optional in
> the way that PEP8 is optional. If I'm reading your annotated code it is
> certainly /not/ optional that I understand the annotations.
>
> * Uploading stubs for other people's code is a terrible idea. Who do I
> contact when I update the interface to my library? The random Joe who
> "helped" by uploading annotations three months ago and then quit the
> internet? I don't even want to think about people maliciously adding stubs
> to PyPI.
>
> * The cognitive load is very high. The average function signature will
> double in length. This is not a small cost and telling me it is "optional"
> to pretend that every other word on the line doesn't exist is a farce.
>
> * Every company's style guide is about to get much longer. That in itself
> is an indicator that this is a MAJOR language change and not just some
> "optional" add-on.
>
> * People will screw it up. The same people who can't be trusted to program
> without type annotations are also going to be *writing* those type
> annotations.
>
> * Teaching python is about to get much less attractive. It will not be
> optional for teachers to say "just pretend all this stuff over here doesn't
> exist"
>
> * "No new syntax" is a lie. Or rather a red herring. There are lots of new
> things it will be required to know and just because the compiler doesn't
> have to change doesn't mean the language isn't undergoing a major change.
>
> If this wasn't in a PEP and it wasn't going to ship in the stdlib very few
> people would use it. If you told everyone they had to install a different
> python implementation they wouldn't. This is much worse than that - it is
> Python4 hidden away inside a PEP.
>
> There are many fine languages that have sophisticated type systems. And
> many bondage & discipline languages that make you type things three times
> to make really really sure you meant to type that. If you find those other
> languages appealing I invite you to go use them instead.
>
> -Jack
>
> https://mail.python.org/pipermail/python-dev/2003-February/033291.html
>
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