On Sat, 19 Mar 2005, Jay Loden wrote:
> How can I prepend something to a list? I thought that I could do
> list.prepend() since you can do list.append() but apparently not. Any
> way to add something to a list at the beginning, or do I just have to
> make a new list?
Hi Jay,
Liam and Sean pointed out that you can either do a combination of
reverse() and append(), or you can use insert().
How often are you planning to prepend onto your lists, though? The
performance of both approaches can be quite different, depending on input
size. Do you plan to do a lot of prepends at a time? Also, are you
dealing with short lists?
If you're dealing with short lists, either solution will work fine. But
if your lists grow to something much larger (say, in the tens of
thousands), then you might need a more specialized solution, such as a
'deque':
http://www.python.org/doc/lib/module-collections.html
A dequeue behaves like a list, but it also supports very fast "prepend"
(in the dequeue documentation, the 'appendleft()' method), so if your
needs are specialized, a deque might be an appropriate data structure for
you.
Best of wishes!
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