lru in python

class LRUCache:
    def __init__(self, capacity):
        self.capacity = capacity
        self.tm = 0
        self.cache = {}
        self.lru = {}

    def get(self, key):
        if key in self.cache:
            self.lru[key] = self.tm
            self.tm += 1
            return self.cache[key]

        return -1

    def set(self, key, value):
        if len(self.cache) >= self.capacity:
            # find the LRU entry
            old_key = min(self.lru.keys(), key = lambda k:self.lru[k])
            self.cache.pop(old_key)
            self.lru.pop(old_key)
        self.cache[key] = value
        self.lru[key] = self.tm
        self.tm += 1

import collections

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

    def get(self, key):
        try:
            value = self.cache.pop(key)
            self.cache[key] = value
            return value
        except KeyError:
            return -1

    def set(self, key, value):
        try:
            self.cache.pop(key)
        except KeyError:
            if len(self.cache) >= self.capacity:
                self.cache.popitem(last=False)
        self.cache[key] = value