[Python-Dev] PEP-xxx: Unification of for statement and list-comp syntax

[Josiah Carlson]

Heiko Wundram <me+python-dev at modelnine.org> wrote:
> 
> Am Sonntag 21 Mai 2006 22:11 schrieb Talin:
> > As a general guideline, I've noticed that proposals which are purely
> > syntactic sugar are unlikely to be accepted unless there is some
> > additional benefit other than just compression of source code.
> 
> I know about this, but generally, I find there's more to this "syntactic 
> sugar" than just source code compression.
> 
> 1) It unifies the syntax for list comprehensions and for loops, which use the 

No, it /partially unifies/ list comprehensions and for loops.  To
actually unify them, you would need to allow for arbitrarily nested fors
and ifs...

for ... in ... [if ...] [for ... in ... [if ...]]*:

If I remember correctly, this was why it wasn't accepted before; because
actual unification is ugly.  Further, because quite literally the only
difference is some indentation, a colon, and a line break, the vast
majority of people would likely stick with "the one obvious way to do it",
which has always worked.


> 2) Just as I've replied to Terry J. Reed, if you find list comprehensions easy 
> to read, you're also bound to be able to understand what "for <expr> in 
> <expr> if <expr>:" does, at least AFAICT.

Not everyone finds list comprehensions easy to read.


> 3) Generally, indentation, as Terry J. Reed suggested, isn't always good. If 
> the body of the loop is more than a few lines long (which happens more often 
> than not in my code), extra indentation is bound to confuse me. That's why I 
[snip]

I feel for you; I really do.  I've done the same thing myself. However,
I don't believe that it is a good practice, in general, and I don't
think that syntax should support this special case.


> And, additionally, nobody's keeping me from making my own Python tree where I 
> can keep this patch for my very personal scripts where I don't need to have 
> interoperability. This is open source, isn't it? ;-)

Do whatever you want.  Good luck with keeping your patches current
against whatever Python version you plan on using.


 - Josiah