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

[Steven D'Aprano]

On Tue, Apr 21, 2015 at 01:25:34PM +0100, Chris Withers wrote:

> Anyway, I've not posted much to python-dev in quite a while, but this is 
> a topic that I would be kicking myself in 5-10 years time when I've had 
> to move to Javascript or <insert new language here> because everyone 
> else has drifted away from Python as it had become ugly...


Facebook released Flow, a static typechecker for Javascript, to a very 
positive reaction. From their announcement:

    Flow’s type checking is opt-in — you do not need to type check all 
    your code at once. However, underlying the design of Flow is the 
    assumption that most JavaScript code is implicitly statically typed; 
    even though types may not appear anywhere in the code, they are in 
    the developer’s mind as a way to reason about the correctness of the 
    code. Flow infers those types automatically wherever possible, which 
    means that it can find type errors without needing any changes to 
    the code at all. On the other hand, some JavaScript code, especially 
    frameworks, make heavy use of reflection that is often hard to 
    reason about statically. For such inherently dynamic code, type 
    checking would be too imprecise, so Flow provides a simple way to 
    explicitly trust such code and move on. This design is validated by 
    our huge JavaScript codebase at Facebook: Most of our code falls in 
    the implicitly statically typed category, where developers can check 
    their code for type errors without having to explicitly annotate 
    that code with types.

Quoted here: 

http://blog.jooq.org/2014/12/11/the-inconvenient-truth-about-dynamic-vs-static-typing/


More about flow: 

http://flowtype.org/


Matz is interested in the same sort of gradual type checking for Ruby as 
Guido wants to add to Python:

https://www.omniref.com/blog/blog/2014/11/17/matz-at-rubyconf-2014-will-ruby-3-dot-0-be-statically-typed/


Julia already includes this sort of hybrid dynamic+static type checking:

http://julia.readthedocs.org/en/latest/manual/types/

I could keep going, but I hope I've made my point. Whatever language you 
are using in 5-10 years time, it will almost certainly be either mostly 
static with some dynamic features like Java, or dynamic with optional 
and gradual typing.



-- 
Steven