How do I implement an LRU cache in Python?

How do I implement an LRU cache in Python?

To implement an LRU (Least Recently Used) cache in Python, you can use the collections.OrderedDict class. This allows you to maintain the order of keys based on their usage.

Can you show me a simple code example?

Sure! Here's a basic implementation:

from collections import OrderedDict

class LRUCache:
    def __init__(self, capacity: int):
        self.cache = OrderedDict()
        self.capacity = capacity

    def get(self, key: int) -> int:
        if key not in self.cache:
            return -1
        else:
            self.cache.move_to_end(key)
            return self.cache[key]

    def put(self, key: int, value: int) -> None:
        if key in self.cache:
            self.cache.move_to_end(key)
        self.cache[key] = value
        if len(self.cache) > self.capacity:
            self.cache.popitem(last=False)

What does the move_to_end method do?

The move_to_end method moves an existing key to the end of the OrderedDict, marking it as recently used. This is crucial for maintaining the LRU order.

How can I test this LRU cache implementation?

You can test it by creating an instance of LRUCache, adding some items, and then accessing them to see if the least recently used item is evicted when the capacity is exceeded.