[Will McGugan]
> I need a collection class that behaves like a dictionary but when it
> reaches 'n' items it discards the oldest item so that the length never
> goes above 'n'. (Its for caching search results)
import collections
class Cache(dict):
def __init__(self, n, *args, **kwds):
self.n = n
self.queue = collections.deque()
dict.__init__(self, *args, **kwds)
def __setitem__(self, k, v):
self.queue.append(k)
dict.__setitem__(self, k, v)
if len(self) > self.n:
oldk = self.queue.popleft()
del self[oldk]
# . . .
# make similar modifications to setdefault, __delitem__, fromkeys
# and other mutating methods as needed
# Example
c = Cache(3)
for w in 'the quick brown fox jumped over the lazy dog'.split():
c[w] = w[:1].upper()
print repr(c)
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