There's SortedDict class from Django source code: http://code.djangoproject.com/browser/django/trunk/django/utils/datastructures.py
class SortedDict(dict):
"""
A dictionary that keeps its keys in the order in which they're inserted.
"""
def __new__(cls, *args, **kwargs):
instance = super(SortedDict, cls).__new__(cls, *args, **kwargs)
instance.keyOrder = []
return instance
def __init__(self, data=None):
if data is None:
data = {}
elif isinstance(data, GeneratorType):
# Unfortunately we need to be able to read a generator twice. Once
# to get the data into self with our super().__init__ call and a
# second time to setup keyOrder correctly
data = list(data)
super(SortedDict, self).__init__(data)
if isinstance(data, dict):
self.keyOrder = data.keys()
else:
self.keyOrder = []
for key, value in data:
if key not in self.keyOrder:
self.keyOrder.append(key)
def __deepcopy__(self, memo):
return self.__class__([(key, deepcopy(value, memo))
for key, value in self.iteritems()])
def __setitem__(self, key, value):
if key not in self:
self.keyOrder.append(key)
super(SortedDict, self).__setitem__(key, value)
def __delitem__(self, key):
super(SortedDict, self).__delitem__(key)
self.keyOrder.remove(key)
def __iter__(self):
return iter(self.keyOrder)
def pop(self, k, *args):
result = super(SortedDict, self).pop(k, *args)
try:
self.keyOrder.remove(k)
except ValueError:
# Key wasn't in the dictionary in the first place. No problem.
pass
return result
def popitem(self):
result = super(SortedDict, self).popitem()
self.keyOrder.remove(result[0])
return result
def items(self):
return zip(self.keyOrder, self.values())
def iteritems(self):
for key in self.keyOrder:
yield key, self[key]
def keys(self):
return self.keyOrder[:]
def iterkeys(self):
return iter(self.keyOrder)
def values(self):
return map(self.__getitem__, self.keyOrder)
def itervalues(self):
for key in self.keyOrder:
yield self[key]
def update(self, dict_):
for k, v in dict_.iteritems():
self[k] = v
def setdefault(self, key, default):
if key not in self:
self.keyOrder.append(key)
return super(SortedDict, self).setdefault(key, default)
def value_for_index(self, index):
"""Returns the value of the item at the given zero-based index."""
return self[self.keyOrder[index]]
def insert(self, index, key, value):
"""Inserts the key, value pair before the item with the given index."""
if key in self.keyOrder:
n = self.keyOrder.index(key)
del self.keyOrder[n]
if n < index:
index -= 1
self.keyOrder.insert(index, key)
super(SortedDict, self).__setitem__(key, value)
def copy(self):
"""Returns a copy of this object."""
# This way of initializing the copy means it works for subclasses, too.
obj = self.__class__(self)
obj.keyOrder = self.keyOrder[:]
return obj
def __repr__(self):
"""
Replaces the normal dict.__repr__ with a version that returns the keys
in their sorted order.
"""
return '{%s}' % ', '.join(['%r: %r' % (k, v) for k, v in self.items()])
def clear(self):
super(SortedDict, self).clear()
self.keyOrder = []
It's a drop-in replacement for built-in dict wherever you need to remember order of insertion.
Right, I have to stop digging here or else I'll start answering to topics from years ago :) |
![[Go to top]](/images/gototop.gif){kind=small}
top