[Sugar-devel] Coding style: line continuations

[Martin Dengler]

On Fri, Nov 12, 2010 at 03:27:15AM +0800, C. Scott Ananian wrote:
> On Fri, Nov 12, 2010 at 2:09 AM, Simon Schampijer <simon at schampijer.de>
> wrote:
> > In general I would do what the spec says if there is no good reason not to
> > [1]. The example they have does not really handle all the cases, though.
> > Neither pep8 nor pylint does favor any formatting. So I guess we are a bit
> > free here.
> 
> I belive PEP8's example is rather definitive:
> 
> "... Make sure to indent the continued line appropriately.  The preferred
> place to break around a binary operator is *after* the operator, not before
> it.[" ...]
> I don't think there's any ambiguity there, actually.

Indeed, so I think we should accept that: it's written down that way
and the issue is otherwise open to legitimate argument (I think it's a
overly prescriptive, though[1]).

>   --scott

Martin

[1] When the boolean logic joining the tests are quite important
relative to the tests themselves, the boolean operators benefit from
emphasis:

if (width == 0
    and height == 0
    and color == 'red'
    and emphasis == 'strong'
    or highlight > 100):

...rather than:

if (width == 0 and
    height == 0 and
    color == 'red' and
    emphasis == 'strong' or
    highlight > 100):

But we can argue about this point for a while.  That example really
sucks, since it uses implicit precedence in ways that are quite liable
to require people to refer to the documentation[2]:

if w and h and c and e or hi:

...if I saw that in code I'd want it changed to:

if (w and h and c and e) or hi:

...which is what it means, not:

if w and h and c and (e or hi):

I had to convince myself:
 
w = False
h = True
c = True
e = True
hi = True

print w and h and c and e or hi
print (w and h and c and e) or hi
print w and h and c and (e or hi)

...yields:
True
True
False

[2]  http://docs.python.org/reference/expressions.html#summary


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