from time import monotonic class LRUCache: def __init__(self, open: callable, *, capacity: int, maxage: float): self.open = open self.capacity = capacity self.maxage = maxage self.cache = [] # Each item is a tuple: (key, handle, timestamp), recent items first def __contains__(self, key): return any(rec[0] == key for rec in self.cache) def __getitem__(self, key): # Take from cache or open a new one for i, (k, f, ts) in enumerate(self.cache): if k == key: self.cache.pop(i) break else: f = self.open(key) # Add/restore to end of cache self.cache.append((key, f, monotonic())) self.expire_items() return f def expire_items(self): ts = monotonic() - self.maxage while len(self.cache) > self.capacity or self.cache and self.cache[-1][2] < ts: self.cache.pop()[1].close() def close(self): self.capacity = 0 self.expire_items()