Guido van Rossum wrote: > On 7/8/07, Walter Dörwald <[EMAIL PROTECTED]> wrote: > [quoting Guido] >> > But I still want to hear of a practical use case for the default here. >> >> In most cases >> >> foo = getitem(iterable, 0, None) >> if foo is not None: >> ... >> >> is simpler than: >> >> try: >> foo = getitem(iterable, 0) >> except IndexError: >> pass >> else: >> ... >> >> Here is a use case from one of my "import XML into the database" scripts: >> >> compid = getitem(root[ns.Company_company_id], 0, None) >> if compid: >> compid = int(compid) >> >> The expression root[ns.company_id] returns an iterator that produces all >> children of the root node that are of the element type company_id. If >> there is a company_id its content will be turned into an int, if not >> None will be used. > > Ahem. I hope you have a better use case for getitem() than that > (regardless of the default issue). I find it clearer to write that as > > try: > compid = root[ns.company_id].next() > except StopIteration: > compid = None > else: > compid = int(compid) > > While this is more lines, it doesn't require one to know about > getitem() on an iterator. This is the same reason why setdefault() was > a mistake -- it's too obscure to invent a compact spelling for it > since the compact spelling has to be learned or looked up.
Well I have used (a Python version of) this getitem() function to implement a library that can match a CSS3 expression against an XML tree. For implementing the nth-child(), nth-last-child(), nth-of-type() and nth-last-of-type() pseudo classes (see http://www.w3.org/TR/css3-selectors/#structural-pseudos) getitem() was very useful. Servus, Walter _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
