Hi,
(NB: I'm just a lurker here, posting for almost the
first time. I may say silly things.)
Le 09/12/2021 à 21:32, deavid a écrit :
Hi, I would like to hear the opinion of Python's community on
enforcing types in the future for the language. I've been using Python
as my main language for everything for around 10 years, until I
started moving to Rust 2 years ago; one of the main factors was types.
Just before moving to Rust I started to use mypy heavily, which I
liked a lot and uncovered tons of potential problems. Now (2 years
later), it seems the situation hasn't changed much; I might be wrong,
so let me know what improvements you think landed in this area in the
last 2-3 years.
I don't follow typing closely at all, but I
do nevertheless see quite a number of typing
PEPs getting accepted. Here are a few recent
ones gathered just by reading the index in PEP 0:
https://www.python.org/dev/peps/pep-0589/
https://www.python.org/dev/peps/pep-0586/
https://www.python.org/dev/peps/pep-0585/
https://www.python.org/dev/peps/pep-0591/
https://www.python.org/dev/peps/pep-0593/
https://www.python.org/dev/peps/pep-0604/
https://www.python.org/dev/peps/pep-0612/
https://www.python.org/dev/peps/pep-0613/
https://www.python.org/dev/peps/pep-0647/
I feel it's possible this topic might cause a lot of passionate
answers, but I just want to hear honest opinions on this.
I firmly believe that Python's future would be better if types were
enforced by default at "compile time" (whatever this means in Python),
with an option/flag to disable this, and integrate MyPy or similar
into the interpreter. I'm fully aware that a transition like this
would be very hard and long, but I don't think it's impossible.
Here's a list of my reasons to think that Python is better if it was
typed:
1) On really big codebases and complex projects, it's very easy to
lose track of what things do. Types help detecting bugs early. (Ask
anyone that has used Rust + Clippy, the amount of errors that are
catched is amazing, programs tend to work on the first try)
2) Libraries are currently the top bottleneck for any team to start
using MyPy/Pytype. Making types mandatory would ensure all libraries
have type support. (If anyone has any other proposal to enforce this,
I would like to hear)
3) IDE integration is way simpler and better with types.
4) The interpreter could take further optimizations if it can prove
that a function or piece of code is guaranteed to have a limited set
of types. This could be used by libraries to have great speed ups that
currently are not possible.
5) Static analysis tools could also benefit from types to gain more
insight on what the code is trying to do.
These are benefits of types in general, but
I don't see clearly how having checks built as
part of the standard CPython interpreter will
increase them. Performance perhaps, but the projects
using annotations to eliminate runtime overhead
are in experimental stage. Asking a genuine
question here: is it actually possible to generate
optimized code that supports all of Python?
What about things like int subclasses? MyPyC
doesn't support them as far as I can see,
and I don't see how it could when trying to
generate optimized code. It might only
optimize int operations when it can prove that
all callers don't pass int subclasses, but this
means recompiling when a new caller does pass
a subclass -- which turns Python into far
more of a compiled language. Or am I missing
something?
On the other hand, with the specializing
adaptive that is the result of the Faster
CPython project, it might become eventually
possible to specialize based on types, and
have a cheaper code path when the annotation
is int that will still fall back to a slower
path when an int subclass instance is passed.
Also, you seem to imply that having typing
more tied to the core language will bring
it more popularity. How will this happen
exactly? People don't like it when you break
their code. If Python 4 causes trouble for
users who don't need/want typing, these users
will not suddenly start using typing, but
simply stay with Python 3. You'd apparently
want to require libraries to be annotated
for them to support Python 4, which means
pain that the ecosystem simply cannot afford,
I think. -- And if the annotations remain
optional, then I guess I don't really understand
how it's going to push people to add them,
especially on large libraries, where this is a
significant endeavor.
All the best,
Jean
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