Fix SortedDict deepcopy Error

[David Blewett <david@…>]

I was using the SortedDict implementation from django/utils/datastructures.py for my own use in a project, and came across a problem when I need to do a deepcopy of a SortedDict object. I consistently got the following error:

Python 2.4:

Python 2.4.4 (#1, Aug 11 2007, 00:45:55)
[GCC 3.4.4 (Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from django.utils.datastructures import SortedDict
>>> from copy import deepcopy
>>> sd = SortedDict({'test': 1})
>>> sd_c = deepcopy(sd)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.4/copy.py", line 204, in deepcopy
    y = _reconstruct(x, rv, 1, memo)
  File "/usr/lib/python2.4/copy.py", line 348, in _reconstruct
    y[key] = value
  File "django/utils/datastructures.py", line 62, in __setitem__
    if key not in self.keyOrder:
AttributeError: 'SortedDict' object has no attribute 'keyOrder'

and 2.5:

Python 2.5.1 (r251:54863, Aug 13 2007, 20:15:26)
[GCC 3.4.4 (Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from django.utils.datastructures import SortedDict
>>> from copy import deepcopy
>>> sd = SortedDict({'test': 1})
>>> sd_c = deepcopy(sd)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/copy.py", line 189, in deepcopy
    y = _reconstruct(x, rv, 1, memo)
  File "/usr/lib/python2.5/copy.py", line 334, in _reconstruct
    y[key] = value
  File "django/utils/datastructures.py", line 62, in __setitem__
    if key not in self.keyOrder:
AttributeError: 'SortedDict' object has no attribute 'keyOrder'

The attached patch implements __deepcopy__ in a way that avoids these errors.

[David Blewett <david@…>]

Patch to django/utils/datastructures.py that implements deepcopy

[David Blewett <david@…>]

On a related note, SortedDict doesn't handle .pop(k[, x]) or .popitem(). Perhaps the Ordered Dictionary from ​http://www.voidspace.org.uk/python/odict.html could be of assistance there?

[Chris Beaven]

Design decision on whether to implement this patch or go with just a better class altogether.

[Malcolm Tredinnick]

With regards to adding all these new methods to SortedDict, it's not really that important. SortedDict is for Django's internal use and it works well for that case. I'll add pop() and popitem(), but let's try to avoid needing to add every method under the sun. Django doesn't need them.

[Malcolm Tredinnick]

(In [6593]) Fixed #5183 -- Added deepcopy, pop() and popitem() to SortedDict. Based on
a patch from David Blewett.