dictionary of dictionaries

[Marc 'BlackJack' Rintsch]

On Sun, 09 Dec 2007 00:35:18 -0800, kettle wrote:

> Hi,
>  I'm wondering what the best practice is for creating an extensible
> dictionary-of-dictionaries in python?
> 
>  In perl I would just do something like:
> 
> my %hash_of_hashes;
> for(my $i=0;$i<10;$i++){
>     for(my $j=0;$j<10;$j++){
> 	${$hash_of_hashes{$i}}{$j} = int(rand(10));
>     }
> }
> 
> but it seems to be more hassle to replicate this in python.  I've
> found a couple of references around the web but they seem cumbersome.
> I'd like something compact.

Use `collections.defaultdict`:

from collections import defaultdict
from random import randint

data = defaultdict(dict)
for i in xrange(11):
    for j in xrange(11):
        data[i][j] = randint(0, 10)

If the keys `i` and `j` are not "independent" you might use a "flat"
dictionary with a tuple of both as keys:

data = dict(((i, j), randint(0, 10)) for i in xrange(11) for j in xrange(11))

And just for completeness: The given data in the example can be stored in a
list of lists of course:

data = [[randint(0, 10) for dummy in xrange(11)] for dummy in xrange(11)]

Ciao,
	Marc 'BlackJack' Rintsch