kj <no.em...@please.post> wrote: > > > Switching from Perl here, and having a hard time letting go... > > Suppose I have an "array" foo, and that I'm interested in the 4th, 8th, > second, and last element in that array. In Perl I could write: > > my @wanted = @foo[3, 7, 1, -1]; > > I was a bit surprised when I got this in Python: > > >>> wanted = foo[3, 7, 1, -1] > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: list indices must be integers
You've just tried to index a list with a tuple... If foo was a dictionary then this might make sense. > Granted, Perl's syntax is often obscure and hard-to-read, but in > this particular case I find it quite transparent and unproblematic, > and the fictional "pythonized" form above even more so. > > The best I've been able to come up with in Python are the somewhat > Perl-like-in-its-obscurity: > > >>> wanted = map(foo.__getitem__, (3, 7, 1, -1)) > > or the clearer but unaccountably sesquipedalian > > >>> wanted = [foo[i] for i in 3, 7, 1, -1] > >>> wanted = [foo[3], foo[7], foo[7], foo[-1]] > > Are these the most idiomatically pythonic forms? Or am I missing > something better? Firstly run "import this" at the python interactive interpreter to remind youself of the philosophical differences between perl and python. I think the philosophy of python is the major reason why it is such a good language. As I transitioned from perl to python it took me a while to let go of perlisms, and get used to writing a little bit more code (usually of the order of a few characters only) but which was much much clearer. Perl is full of cleverness which give you great pleasure to write as a programmer. However when you or someone else looks at that code later they don't get that same pleasure - horror is more likely the reaction! Python just isn't like that. I'd probably write wanted = foo[3], foo[7], foo[1], foo[-1] (assuming you didn't mind having a tuple rather than a list) or maybe this wanted = [ foo[i] for i in 3, 7, 1, -1 ] However I can't think of the last time I wanted to do this - array elements having individual purposes are usually a sign that you should be using a different data structure. -- Nick Craig-Wood <n...@craig-wood.com> -- http://www.craig-wood.com/nick -- http://mail.python.org/mailman/listinfo/python-list
