How do I implement an LFU cache in Python?

How do I implement an LFU cache in Python?

To implement an LFU (Least Frequently Used) cache in Python, you can use a combination of a dictionary and a priority queue. Would you like a code example?

Yes, please provide a code example.

Here's a simple implementation:

class LFUCache:
    def __init__(self, capacity: int):
        self.capacity = capacity
        self.cache = {}  # key -> (value, frequency)
        self.freq = {}   # frequency -> keys
        self.min_freq = 0

    def get(self, key: int) -> int:
        if key not in self.cache:
            return -1
        value, freq = self.cache[key]
        self.cache[key] = (value, freq + 1)
        self.freq[freq].remove(key)
        if not self.freq[freq]:
            del self.freq[freq]
            if self.min_freq == freq:
                self.min_freq += 1
        self.freq.setdefault(freq + 1, []).append(key)
        return value

    def put(self, key: int, value: int) -> None:
        if self.capacity <= 0:
            return
        if key in self.cache:
            self.cache[key] = (value, self.cache[key][1])
            self.get(key)  # Update frequency
            return
        if len(self.cache) >= self.capacity:
            lfu_key = self.freq[self.min_freq][0]
            del self.cache[lfu_key]
            self.freq[self.min_freq].pop(0)
            if not self.freq[self.min_freq]:
                del self.freq[self.min_freq]
        self.cache[key] = (value, 1)
        self.freq.setdefault(1, []).append(key)
        self.min_freq = 1

What are the advantages of using an LFU cache?

The LFU cache is efficient for scenarios where certain items are accessed more frequently than others, helping to optimize memory usage and improve performance by keeping the most relevant data.