Python 2.7 and 3.1 have OrderedDict and there are pure-Python implementations for earlier Pythons.
from collections import OrderedDict
class LimitedSizeDict(OrderedDict):
def __init__(self, *args, **kwds):
self.size_limit = kwds.pop("size_limit", None)
OrderedDict.__init__(self, *args, **kwds)
self._check_size_limit()
def __setitem__(self, key, value):
OrderedDict.__setitem__(self, key, value)
self._check_size_limit()
def _check_size_limit(self):
if self.size_limit is not None:
while len(self) > self.size_limit:
self.popitem(last=False)
You would also have to override other methods that can insert items, such as update
. The primary use of OrderedDict
is so you can control what gets popped easily, otherwise a normal dict
would work.