Comments on: Python list implementation

By: dan

dan — Mon, 23 Apr 2012 15:31:04 +0000

tem: agreed. I think the python wiki article can be misleading if you don’t read carefully. pop(0) becomes equivalent to remove, which is O(n) for a basic list.

By: Jan

Jan — Wed, 15 Feb 2012 15:37:53 +0000

Very interesting reading indeed, thanks a lot I found an article about list comlexity, but these memory pictures are really helpful from the point of view of implementation

By: Laurent Luce

Laurent Luce — Tue, 11 Oct 2011 05:45:57 +0000

A list object contains a list of pointers to PyObjects. A PyObject contains a pointer to the corresponding type object. See object.h in the Python source code for more details.

By: Ganesh

Ganesh — Sun, 11 Sep 2011 17:59:01 +0000

Can you explain how is list implemented so as it can hold different datatypes.

By: tem

tem — Mon, 14 Mar 2011 12:49:30 +0000

L.pop([index]) -> item — remove and return item at index.

I’m guessing pop is O(n) if you pop the first element.

By: Laurent Luce

Laurent Luce — Mon, 14 Mar 2011 00:27:19 +0000

@Ivan: I updated the article with the following information. Append is O(1), Insert is O(n), Pop is O(1), Remove is O(n). Sort is O(n log n). You can see more of those here. Appending n elements is O(n). For n = 1000, the list is going to be resized 27 times. The growth pattern is the following: 4, 8, 16, 25, 35, 46, 58, 72, 88, 106, 126, 148, 173, 201, 233, 269, 309, 354, 405, 462, 526, 598, 679, 771, 874, 990, 1120. This means 27 calls to realloc. It doesn't change the complexity. It is still O(n).

By: Ivan

Ivan — Sat, 12 Mar 2011 20:41:10 +0000

Hi,

Could you give us an idea of the running time of these operations?

O(1) for append ?
O(n) for insert ?

And what would be the total running time to append 1000 elements to a [] taking into account operations wasted on growing the list?

By: klonuo

klonuo — Fri, 11 Mar 2011 11:44:58 +0000

Very interesting article

I read it in my RSS reader as part of “Planet Python” feeds and was then “forced” to launch Firefox and see your blog

I hope for other interesting post in future

Cheers

By: TechnoBits.net

TechnoBits.net — Fri, 11 Mar 2011 05:53:26 +0000

Very good article, uncovers the most used feature in python.