The Cost of Dynamism (was Re: Pyhon 2.x or 3.x, which is faster?)

[Jon Ribbens]

On 2016-03-24, BartC <bc at freeuk.com> wrote:
> On 24/03/2016 14:08, Jon Ribbens wrote:
>> if you thought you needed to do that then most likely what you
>> should actually be doing is re-writing your code so you no longer
>> need to. However, you could do:
>>
>>    L[:] = [0] * len(L)
>
> OK, but that's just building a new list as I've already mentioned.

No it isn't, it's replacing the elements in-place, that's what the
"L[:]" bit means. Replacing the list object itself would be:
L = [0] * len(L)

> Or is the Pythonic way, when you want to change some elements of a list 
> to just build a new one that incorporates those changes?

I think it would depend on how many elements you were changing and
why. It doesn't come up all that often because of the ease in which
Python functions can return multiple values but sometimes you might
make a function which takes as a parameter a list which the function
will mutate.