Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.

get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.

set(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.

from collections import OrderedDict

class LastUpdatedOrderedDict(OrderedDict):
    def __setitem__(self, key, value):
        if key in self:
            del self[key]
        OrderedDict.__setitem__(self, key, value)

class LRUCache(object):
    def __init__(self, capacity):
        self.dict = LastUpdatedOrderedDict()
        self.capacity = capacity

    def get(self, key):
        if key in self.dict:
            r = self.dict[key]
            self.dict[key] = r
            return r
        return -1

    def set(self, key, value):
        if key not in self.dict and self.capacity == len(self.dict):
            item = self.dict.popitem(last=False)
        self.dict[key] = value