odict 1.2.5

Ordered dictionary.

odict

Dictionary in which the insertion order of items is preserved (using an internal double linked list). In this implementation replacing an existing item keeps it at its original position.

Internal representation: values of the dict:

[pred_key, val, succ_key]

The sequence of elements uses as a double linked list. The links are dict keys. self.lh and self.lt are the keys of first and last element inseted in the odict. In a C reimplementation of this data structure, things can be simplified (and speed up) a lot if given a value you can at the same time find its key. With that, you can use normal C pointers.

Memory used (Python 2.5)

-set(int): 28.2 bytes/element

-dict(int:None): 36.2 bytes/element

-odict(int:None): 102 bytes/element

Performance

When running the benchmark script, you get results similar to the one below on recent common hardware.

Adding and deleting dict objects.

+----------------+--------------------+
| Add 1000       | 0.000653028488159  |
+----------------+--------------------+
| Delete 1000    | 0.000339031219482  |
+----------------+--------------------+
| Add 10000      | 0.00774908065796   |
+----------------+--------------------+
| Delete 10000   | 0.00406503677368   |
+----------------+--------------------+
| Add 100000     | 0.130412101746     |
+----------------+--------------------+
| Delete 100000  | 0.0517508983612    |
+----------------+--------------------+
| Add 1000000    | 3.17614817619      |
+----------------+--------------------+
| Delete 1000000 | 0.564585924149     |
+----------------+--------------------+

Adding and deleting odict objects.

+----------------+--------------------+
| Add 1000       | 0.0096800327301    |
+----------------+--------------------+
| Delete 1000    | 0.00276303291321   |
+----------------+--------------------+
| Add 10000      | 0.107849836349     |
+----------------+--------------------+
| Delete 10000   | 0.0282921791077    |
+----------------+--------------------+
| Add 100000     | 1.05564808846      |
+----------------+--------------------+
| Delete 100000  | 0.297379016876     |
+----------------+--------------------+
| Add 1000000    | 16.451695919       |
+----------------+--------------------+
| Delete 1000000 | 3.03641605377      |
+----------------+--------------------+

Relation dict:odict of creating and deleting.

+---------------------------+-----------+
| creating 1000 objects     | 1:14.823  |
+---------------------------+-----------+
| deleting 1000 objects     | 1:8.1497  |
+---------------------------+-----------+
| creating 10000 objects    | 1:13.917  |
+---------------------------+-----------+
| deleting 10000 objects    | 1:6.9598  |
+---------------------------+-----------+
| creating 100000 objects   | 1:8.0947  |
+---------------------------+-----------+
| deleting 100000 objects   | 1:5.7463  |
+---------------------------+-----------+
| creating 1000000 objects  | 1:5.1797  |
+---------------------------+-----------+
| deleting 1000000 objects  | 1:5.3781  |
+---------------------------+-----------+

Usage

Import and create ordered dictionary.

>>> from odict import odict
>>> od = odict()

type conversion to ordinary dict. This will fail.

>>> dict(odict([(1, 1)]))
{1: [nil, 1, nil]}

The reason for this is here -> http://bugs.python.org/issue1615701

The __init__ function of dict checks wether arg is subclass of dict, and ignores overwritten __getitem__ & co if so.

This was fixed and later reverted due to behavioural problems with pickle.

Use one of the following ways for type conversion.

>>> dict(odict([(1, 1)]).items())
{1: 1}

>>> odict([(1, 1)]).as_dict()
{1: 1}

Requires

-Python 2.4+

Changes

Version 1.2.5

-Add as_dict function. Supports type conversion to ordinary dict.

rnix, 2009-12-19

-Add benchmark script

rnix, 2009-12-19

Version 1.2.4

-Do not check for key in self on __delitem__, KeyError is raised

properly anyway. Huge Speedup! rnix, jensens, 2009-12-18

Version 1.2.3

-Move tests to seperate file and make egg testable with

python setup.py test. rnix, 2009-12-07

-improve lt and lh properties to make odict work with

copy.deepcopy. rnix, 2009-12-07

Version 1.2.2

-Use try/except instead of __iter__ in __setitem__ to determine if

value was already set. rnix, 2009-07-17

Version 1.2.1

-Add missing __len__ and __contains__ functions.

rnix, 2009-03-17

Version 1.2.0

-eggified

rnix, 2009-03-17

Version < 1.2

-http://code.activestate.com/recipes/498195/

bearophile, 2006-10-12

Credits

-bearophile

-Robert Niederreiter <[e-mail]>