Python Lists(Slice method)

Question

I am a newbie to python,everywhere I read about list methods I see one thing

The slice method returns a "new" list

What is here meant by "new" list,and why is it faster then changing the original list?

Does it really matter if python manipulates the original list,I mean I cant use it anyway.

Answer 1

With lists, you can do both:

1) create a new list (the original is left intact):

In [1]: l = [1, 2, 3, 4, 5]

In [2]: l[:3]
Out[2]: [1, 2, 3]

In [3]: l
Out[3]: [1, 2, 3, 4, 5]

2) modify the list in-place:

In [6]: del l[3:]

In [7]: l
Out[7]: [1, 2, 3]

In [8]: l.append(15)

In [9]: l
Out[9]: [1, 2, 3, 15]

It's up to you to choose which way makes more sense for your problem.

In contrast to lists, tuples are immutable, which means that you can slice them, but you cannot modify them in place.