Is there a better/simpler way to filter blank lines?

Lie Lie.1296 at gmail.com
Wed Nov 5 22:16:18 CET 2008


On Nov 5, 4:56 pm, Marc 'BlackJack' Rintsch <bj_... at gmx.net> wrote:
> On Wed, 05 Nov 2008 14:39:36 +1100, Ben Finney wrote:
> > Marc 'BlackJack' Rintsch <bj_... at gmx.net> writes:
>
> >> On Wed, 05 Nov 2008 13:18:27 +1100, Ben Finney wrote:
>
> >> > Marc 'BlackJack' Rintsch <bj_... at gmx.net> writes:
>
> >> > Your example shows only that they're important for grouping the
> >> > expression from surrounding syntax. As I said.
>
> >> > They are *not* important for making the expresison be a generator
> >> > expression in the first place. Parentheses are irrelevant for the
> >> > generator expression syntax.
>
> >> Okay, technically correct but parenthesis belong to generator
> >> expressions because they have to be there to separate them from
> >> surrounding syntax with the exception when there are already enclosing
> >> parentheses.  So parenthesis are tied to generator expression syntax.
>
> > No, I think that's factually wrong *and* confusing.
>
> >     >>> list(i + 7 for i in range(10))
> >     [7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
>
> > Does this demonstrate that parentheses are “tied to” integer literal
> > syntax? No.
>
> You can use integer literals without parenthesis, like the 7 above, but
> you can't use generator expressions without them.  They are always
> there.  In that way parenthesis are tied to generator expressions.
>
> If I see the pattern ``f(x) for x in obj if c(x)`` I look if it is
> enclosed in parenthesis or brackets to decide if it is a list
> comprehension or a generator expression.  That may not reflect the formal
> grammar, but it is IMHO the easiest and pragmatic way to look at this as
> a human programmer.
>
> Ciao,
>         Marc 'BlackJack' Rintsch

The situation is similar to tuples. What makes a tuple is the commas,
not the parens.
What makes a generator expression is "<exp> for <var-or-tuple> in
<exp>".

Parenthesis is generally required because without it, it's almost
impossible to differentiate it with the surrounding. But it is not
part of the formally required syntax.



More information about the Python-list mailing list