On Aug 25, 10:46 pm, Falcolas <garri...@gmail.com> wrote: > On Aug 25, 1:58 pm, seb <sdemen...@gmail.com> wrote: > > > On Aug 25, 9:42 pm, Falcolas <garri...@gmail.com> wrote: > > > On Aug 25, 11:25 am, seb <sdemen...@gmail.com> wrote: > > > So, what part of the statement does the "if" statement belong to; > > > particularly a concern considering this is valid python: > > > > for x in y if y else z: > > > body > > > can this be done in list/set/dict comprehensions/generator > > expressions ? > > It's a statement, so anywhere you use a statement (such as in > generators and list comprehensions), it can exist. for ... in ... only > requires that the statement return an iterable, it doesn't matter what > statement you use to get there. >
I never thought about this case... Testing that in python 3.0, i see that >>> [x for x in range(5) if False else range(10)] SyntaxError: invalid syntax (<pyshell#17>, line 1) >>> [x for x in (range(5) if False else range(10))] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] hence, to avoid the ambiguity you mentionned (that already exists with list comprehensions), one can use the parenthesis. This minor incompatibility is referenced in http://www.python.org/dev/peps/pep-0308/ > It doesn't feel clear to me, which is why I would have to disagree. > IIRC, these very filters are the main reason that list comprehensions, > and later one-line generators and dictionary comprehensions were > originally created: so you can filter the stream before acting on it. > One statement performs one action - very precise and understandable. in my mind, I am thinking as you are but with 'loop' instead of 'stream' """so you can filter the 'loop' before acting on it. One statement performs one action - very precise and understandable.""" and it doesn't look that dissimilar to your own reasoning. > > It's just my two cents, but I would not agree that adding a filter > keyword to for loops is required. Not when we have the filter > function, various types of comprehensions, and if statements which all > provide that very functionality. > before having list comprehensions, we could also have said that """ I would not agree that adding a 'list comprehension' feature is required. Not when we have the filter function, and the 'for+if' statements which all provide that very functionality.""" How can unifying the "for ... in ..." statement with the "for ... in ... if ..." syntax be detrimental ? It would be an inconsistence less to remember, wouldn't it ? cheers, sebastien -- http://mail.python.org/mailman/listinfo/python-list
