Class odict

source code

object --+    
         |    
      dict --+
             |
            odict

Ordered dict example implementation.

This is the proposed interface for a an ordered dict as proposed on the Python mailinglist (proposal).

It's a dict subclass and provides some list functions. The implementation of this class is inspired by the implementation of Babel but incorporates some ideas from the ordereddict and Django's ordered dict.

The constructor and update() both accept iterables of tuples as well as mappings:

>>> d = odict([('a', 'b'), ('c', 'd')])
>>> d.update({'foo': 'bar'})
>>> d
odict.odict([('a', 'b'), ('c', 'd'), ('foo', 'bar')])

Keep in mind that when updating from dict-literals the order is not preserved as these dicts are unsorted!

You can copy an odict like a dict by using the constructor, copy.copy or the copy method and make deep copies with copy.deepcopy:

>>> from copy import copy, deepcopy
>>> copy(d)
odict.odict([('a', 'b'), ('c', 'd'), ('foo', 'bar')])
>>> d.copy()
odict.odict([('a', 'b'), ('c', 'd'), ('foo', 'bar')])
>>> odict(d)
odict.odict([('a', 'b'), ('c', 'd'), ('foo', 'bar')])
>>> d['spam'] = []
>>> d2 = deepcopy(d)
>>> d2['spam'].append('eggs')
>>> d
odict.odict([('a', 'b'), ('c', 'd'), ('foo', 'bar'), ('spam', [])])
>>> d2
odict.odict([('a', 'b'), ('c', 'd'), ('foo', 'bar'), ('spam', ['eggs'])])

All iteration methods as well as keys, values and items return the values ordered by the the time the key-value pair is inserted:

>>> d.keys()
['a', 'c', 'foo', 'spam']
>>> d.values()
['b', 'd', 'bar', []]
>>> d.items()
[('a', 'b'), ('c', 'd'), ('foo', 'bar'), ('spam', [])]
>>> list(d.iterkeys())
['a', 'c', 'foo', 'spam']
>>> list(d.itervalues())
['b', 'd', 'bar', []]
>>> list(d.iteritems())
[('a', 'b'), ('c', 'd'), ('foo', 'bar'), ('spam', [])]

Index based lookup is supported too by byindex which returns the key/value pair for an index:

>>> d.byindex(2)
('foo', 'bar')

You can reverse the odict as well:

>>> d.reverse()
>>> d
odict.odict([('spam', []), ('foo', 'bar'), ('c', 'd'), ('a', 'b')])

And sort it like a list:

>>> d.sort(key=lambda x: x[0].lower())
>>> d
odict.odict([('a', 'b'), ('c', 'd'), ('foo', 'bar'), ('spam', [])])

new empty dictionary