# 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.

```