[Python-Dev] PEP 471 -- os.scandir() function -- a better and faster directory iterator

[Paul Sokolovsky]

Hello,

On Fri, 27 Jun 2014 12:08:41 +1000
Steven D'Aprano <steve at pearwood.info> wrote:

> On Fri, Jun 27, 2014 at 03:07:46AM +0300, Paul Sokolovsky wrote:
> 
> > With my MicroPython hat on, os.scandir() would make things only
> > worse. With current interface, one can either have inefficient
> > implementation (like CPython chose) or efficient implementation
> > (like MicroPython chose) - all transparently. os.scandir()
> > supposedly opens up efficient implementation for everyone, but at
> > the price of bloating API and introducing heavy-weight objects to
> > wrap info. 
> 
> os.scandir is not part of the Python API, it is not a built-in
> function. It is part of the CPython standard library. 

Ok, so standard library also has API, and that's the API being
discussed. 

> That means (in
> my opinion) that there is an expectation that other Pythons should
> provide it, but not an absolute requirement. Especially for the os
> module, which by definition is platform-specific. 

Yes, that's intuitive, but not strict and formal, so is subject to
interpretations. As a developer working on alternative Python
implementation, I'd like to have better understanding of what needs to
be done to be a compliant implementation (in particular, because I need
to pass that info down to the users). So, I was told that
https://docs.python.org/3/reference/index.html describes Python, not
CPython. Next step is figuring out whether 
https://docs.python.org/3/library/index.html describes Python or
CPython, and if the latter, how to separate Python's stdlib essence from
extended library CPython provides?

> In my opinion that
> means you have four options:
> 
> 1. provide os.scandir, with exactly the same semantics as on CPython;
> 
> 2. provide os.scandir, but change its semantics to be more
> lightweight (e.g. return an ordinary tuple, as you already suggest);
> 
> 3. don't provide os.scandir at all; or
> 
> 4. do something different depending on whether the platform is Linux
>    or an embedded system.
> 
> I would consider any of those acceptable for a library feature, but
> not for a language feature.

Good, thanks. If that represents shared opinion of (C)Python developers
(so, there won't be claims like "MicroPython is not Python because it
doesn't provide os.scandir()" (or hundred of other missing stdlib
functions ;-) )) that's good enough already.

With that in mind, I wished that any Python implementation was as
complete and as efficient as possible, and one way to achieve that is
to not add stdlib entities without real need (be it more API calls or
more data types). So, I'm glad to know that os.scandir() passed thru
Occam's Razor in this respect and specified the way it is really for
common good.


[]

-- 
Best regards,
 Paul                          mailto:pmiscml at gmail.com