[Buildroot] [PATCH 10/19] support: rewrite check-bin-arch in python

[Yann E. MORIN]

Thomas DS, All,

On 2019-01-08 18:22 +0100, Thomas De Schampheleire spake thusly:
> El mar., 8 ene. 2019 a las 17:37, Yann E. MORIN
> (<yann.morin.1998 at free.fr>) escribió:
[--SNIP--]
> > > Note that I think that performance will be better with a list
> > > comprehension instead of explicit for's. Something like (untested):
> > >
> > > valid_records = [ record for record in parse_pkg_file_list(args.pkg_list)
> > >             if record['pkg'] == args.package
> > >             and not any(ignore_re.match(record['file']) for ignore_re
> > > in ignores_re) ]
> >
> > Sorry, but this is totally illegible to me.
> 
> :-D
> 
> Ok, I won't argue about the fact itself.
> Just, as a reference, small decomposition:
> 
> list = [ f(x) for x in otherlist ]
> 
> is a 'list comprehension' and is a performant way to generate a list
> without requiring a for loop.
> f(x) can be any action on x, e.g. x.strip() or more complex
> expressions involving x.

Yeah, I know what it is [0], and I can actually decipher the code above
with quite a bit of mental processing. But that is it: it's deciphering,
not reading.

[0] I even use them: https://patchwork.ozlabs.org/patch/1021622/

[--SNIP--]
> Here, any(x) is a function that takes an iterable (x) and returns True
> if any of the items in 'x' evaluate to True.

Ah, I did not know about any() (although I did infer its behaviour from
its name!) Thanks! :-)

> Similar to any(x) there is also all(x) which only returns True if
> _all_ items in x evaluate to True.

And is there none() ? ;-) I guess it's "not all()"...

> The value passed to 'any' is '(ignore_re.match(record['file']) for
> ignore_re in ignores_re)'
> which itself is a type of list comprehension, except that it actually
> is a generator comprehension. 'generator' is what you called an
> 'iterator' in another patch: a thing that 'yields' values one by one.

Yep, generator, not iterator.

[--SNIP--]
> I hope it makes things a bit more clear :)

As I said, I can actually decipher it (well, once the indentation if
fixed anyway! ;-) ), but still it is less readable for me...

And since I would have hard a time justifying it, or would have a hard
time maintaining it in the future, I prefer writing (and thus keeping)
code that I can work with later.

If others find the comprehensions easier to comprehend (pun), then fine,
but I would be much less at ease with that.

Thanks! :-)

Regards,
Yann E. MORIN.

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