[Scons-users] Is this a feature or a bug
(

[Kyle J Strand]

I agree that from a user perspective, the third argument should be any 
iterable, but I'd be willing to bet that the tuple is in fact being turned 
into a single-item list somewhere in the code. This is a hazard of the "if 
not isinstance(inputarg, list): inputarg = [inputarg]" pattern that seems 
to show up a lot in the SCons code (and arguably a hazard of ever using 
"isinstance"). While this is certainly a very Pythonic issue to be running 
into, I don't think it would be "unPythonic" in the least to fix it. But 
that might be a question better suited to the dev list.

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Kyle Strand, Software Intern
Beckman Coulter, Inc., Life Sciences Division
4862 Innovation Drive, Fort Collins, Colorado, 80525
(970) 204-7036

scons-users-bounces at scons.org wrote on 08/21/2012 01:14:48 PM:


> William Deegan <bill at baddogconsulting.com> 

> Sent by: scons-users-bounces at scons.org

> 

> 08/21/2012 01:14 PM

> 

> Please respond to

> SCons users mailing list <scons-users at scons.org>

> 

> To

> 

> scons-users at scons.org

> 

> cc

> 

> Subject

> 

> Re: [Scons-users] Is this a feature or a bug…

> 

> On 08/21/2012 08:40 AM, Chris BeHanna wrote:

> > On Aug 21, 2012, at 10:04 , Gary Oberbrunner <garyo at oberbrunner.com> 

wrote:

> >

> >> On Tue, Aug 21, 2012 at 10:44 AM, Russel Winder 

> <russel at winder.org.uk> wrote:

> >>> Just asking the question prior to putting in a bug report, just in 

case

> >>> I have missed something…

> >>>

> >>> Command(XXX, YYY, [AAA, BBB])

> >>>

> >>> i.e. the action sequence is a list, works fine.  However,

> >>>

> >>> Command(XXX, YYY, (AAA, BBB))

> >>>

> >>> is reported as an error, i.e. a tuple is not acceptable where a list 

is.

> >>>

> >>> To say this doesn't violate the Principle of Least Surprise would be 

to

> >>> violate the Principle of Least Surprise.

> >> I can't see any particular reason we shouldn't support tuples as well

> >> as lists there, although actually doing it might be complicated.

> >    A tuple, strictly speaking, is not *exactly* the same as a list

> in python.  What you might have happen is this:

> >

> >    Command(XXX, YYY, (AAA, BBB))

> >

> > gets translated by layers below as

> >

> >    Command(XXX, YYY, [(AAA,BBB)])

> >

> > i.e., that tuple becomes a singleton dictionary with a single key-

> value pair, rather than a list with two elements.

> >

> >    Thus, I would disagree, looking at it from a strictly 

> "pythonic" view, that it violates POLA.  I would actually expect it 

> not to work properly.

> >

> Likely the third argument should allow any iterable.

> So it could be a generator even.

> The contents of a single element would be what you'd then have to check 

> to see if they matched what was expected. (To address your [(aaa,bbb)] 

> above.)

> 

> 

> -Bill

> 

> _______________________________________________

> Scons-users mailing list

> Scons-users at scons.org

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