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

Josiah Carlson jcarlson at uci.edu
Mon May 22 01:59:25 CEST 2006

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 in if :" 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.

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