implement lru cache in Python

from collections import OrderedDict

class LRUCache:

    # initialising capacity
    def __init__(self, capacity: int):
        self.cache = OrderedDict()
        self.capacity = capacity

    # we return the value of the key
    # that is queried in O(1) and return -1 if we
    # don't find the key in out dict / cache.
    # And also move the key to the end
    # to show that it was recently used.
    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]

    # first, we add / update the key by conventional methods.
    # And also move the key to the end to show that it was recently used.
    # But here we will also check whether the length of our
    # ordered dictionary has exceeded our capacity,
    # If so we remove the first key (least recently used)
    def put(self, key: int, value: int) -> None:
        self.cache[key] = value
        self.cache.move_to_end(key)
        if len(self.cache) > self.capacity:
            self.cache.popitem(last = False)

if __name__ == "__main__":
cache = LRUCache(3)
cache.put(1, 1)
print(cache.cache)
cache.put(2, 1)
print(cache.cache)
cache.get(1)
print(cache.cache)
cache.put(3, 3)
print(cache.cache)
cache.get(2)
print(cache.cache)
cache.put(4, 4)
print(cache.cache)
cache.get(1)
print(cache.cache)
cache.get(3)
print(cache.cache)
cache.get(4)
print(cache.cache)

or

import collections


class ListNode:

    def __init__(self, key, val):
        self.val = val
        self.key = key
        self.next = None
        self.prev = None


class LinkedList:

    def __init__(self):
        self.head = None
        self.tail = None

    def insert(self, node):
        if self.head is None:
            self.head = node
        else:
            self.tail.next = node
            node.prev = self.tail
        self.tail = node

    def delete(self, node):
        if node.prev:
            node.prev.next = node.next
        else:
            self.head = node.next
        if node.next:
            node.next.prev = node.prev
        else:
            self.tail = node.prev
        del node


class LRUCache:

    def __init__(self, capacity):
        self.list = LinkedList()
        self.dict = {}
        self.capacity = capacity

    def _insert(self, key, val):
        node = ListNode(key, val)
        self.list.insert(node)
        self.dict[key] = node

    def get(self, key):
        if key in self.dict:
            val = self.dict[key].val
            self.list.delete(self.dict[key])
            self._insert(key, val)
            return val
        return -1

    def set(self, key, val):
        if key in self.dict:
            self.list.delete(self.dict[key])
        elif len(self.dict) == self.capacity:
            del self.dict[self.list.head.key]
            self.list.delete(self.list.head)
        self._insert(key, val)


class LRUCache2:
    def __init__(self, capacity):
        self.cache = collections.OrderedDict()
        self.capacity = capacity

    def get(self, key):
        if key not in self.cache:
            return -1
        val = self.cache[key]
        del self.cache[key]
        self.cache[key] = val
        return val

    def set(self, key, value):
        if key in self.cache:
            del self.cache[key]
        elif len(self.cache) == self.capacity:
            self.cache.popitem(last=False)
        self.cache[key] = value


if __name__ == "__main__":
    cache = LRUCache(3)
    # cache = LRUCache2(3)
    cache.set(1, 1)
    cache.set(2, 2)
    cache.set(3, 3)
    print(cache.get(1))
    cache.set(4, 4)
    print(cache.get(2))