Memory pre-allocation for large lists

[Avi Kak]

Hello:

Is it possible in Python to define an empty list
of a predetermined size?

To illustrate my question further, I can do the
following in Perl

my @arr = ();
$#arr = 999;

that wold cause @arr to become an empty array
of size 1000. This array could be used to
store 1000 elements without any further memory
allocation for the array itself.

Can the same be done in Python?

Avi Kak
kak@purdue.edu

[Erik Max Francis]

Re: Memory pre-allocation for large lists

Avi Kak wrote:
[color=blue]
> Can the same be done in Python?[/color]

Not directly, but you can just fill it with something you're not going
to use:

arra = [None] * 999

--
__ Erik Max Francis && max@alcyone.com && http://www.alcyone.com/max/
/ \ San Jose, CA, USA && 37 20 N 121 53 W && &tSftDotIotE
\__/ Of war men ask the outcome, not the cause.
-- Seneca

[Avi Kak]

Re: Memory pre-allocation for large lists



Thanks, Erik. That would work for me.

Avi


On Tue, 17 Feb 2004 22:00:09 -0800, Erik Max Francis <max@alcyone.co m>
wrote:
[color=blue]
>Avi Kak wrote:
>[color=green]
>> Can the same be done in Python?[/color]
>
>Not directly, but you can just fill it with something you're not going
>to use:
>
> arra = [None] * 999[/color]

[Aahz]

Re: Memory pre-allocation for large lists

In article <ift530d51l8td0 uoohm5t9ad96pq5 n4e3i@4ax.com>,
Avi Kak <kak@purdue.edu > wrote:[color=blue]
>
>Is it possible in Python to define an empty list of a predetermined
>size?
>
>To illustrate my question further, I can do the following in Perl
>
> my @arr = ();
> $#arr = 999;
>
>that wold cause @arr to become an empty array of size 1000. This
>array could be used to store 1000 elements without any further memory
>allocation for the array itself.
>
>Can the same be done in Python?[/color]

Can, yes. But why? Python uses an allocation mechanism for lists that
results in constant amortized time; there's really no reason to
pre-allocate.
--
Aahz (aahz@pythoncra ft.com) <*> http://www.pythoncraft.com/

"Argue for your limitations, and sure enough they're yours." --Richard Bach