Gabriel Genellina wrote: > En Wed, 07 Mar 2007 12:53:43 -0300, Laurent Pointal > <[EMAIL PROTECTED]> escribió: > >>>>> f(4,i for i in range(10)) >> File "<stdin>", line 1 >> SyntaxError: invalid syntax > > 2.5 has a better error message: > py> f(4,i for i in range(10)) > File "<stdin>", line 1 > SyntaxError: Generator expression must be parenthesized if not sole > argument > >> Why does Python allow generator expression parenthesis to be mixed with >> function call parenthesis when there is only one parameter ? > > Because they are redundant when only one argument is used. > sum(i for i in range(10)) looks better than sum((i for i in range(10))) > "Beautiful is better than ugly", and "Readability counts."
I complement my reply. Beginners generally know about list-comprehensions and associate the syntax "x for x in asequence" to a list expression. I'm not sure that reading a "f(i for i in range(20))" they understand that they are dealing with a different object kind. If function f start by a if len(myparameter)... TypeError: len() of unsized object If function f goes among its parameter with "for x in myparameter" more than once, other loops goes throught an empty loop. >> IMHO this should be forbidden, usage must not be different when there is >> only one parameter and when there are more parameters. > > It's similar to "%d" % 123 vs. "%d" % (123,) > """Special cases aren't special enough to break the rules. > Although practicality beats purity.""" In that case there cannot be confusion. A+ Laurent. -- http://mail.python.org/mailman/listinfo/python-list
