Op 2005-12-10, Devan L schreef <[EMAIL PROTECTED]>: > > Antoon Pardon wrote: >> On 2005-12-10, Duncan Booth <[EMAIL PROTECTED]> wrote: > [snip] >> >> I also think that other functions could benefit. For instance suppose >> >> you want to iterate over every second element in a list. Sure you >> >> can use an extended slice or use some kind of while. But why not >> >> extend enumerate to include an optional slice parameter, so you could >> >> do it as follows: >> >> >> >> for el in enumerate(lst,::2) >> > >> > 'Why not'? Because it makes for a more complicated interface for something >> > you can already do quite easily. >> >> Do you think so? This IMO should provide (0,lst[0]), (2,lst[2]), >> (4,lst[4]) ... >> >> I haven't found a way to do this easily. Except for something like: >> >> start = 0: >> while start < len(lst): >> yield start, lst[start] >> start += 2 >> >> But if you accept this, then there was no need for enumerate in the >> first place. So eager to learn something new, how do you do this >> quite easily? > >>>> lst = ['ham','eggs','bacon','spam','foo','bar','baz'] >>>> list(enumerate(lst))[::2] > [(0, 'ham'), (2, 'bacon'), (4, 'foo'), (6, 'baz')]
It is not about what is needed, but about convenience. Now let me see, in order to just iterate over the even elements of a list with the index of the element, you turned an iterator into a list, which you use to create an other list which you will finaly iterate over. If this is the proposed answer, I wonder why iterators were introduced in the first place. I thought iterator were went to avoid the need to construct and copy list when all you want is iterate and when I ask how to get a specific iterator you come with a construct that makes rather heavily use of list constructions. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
