mirror of
https://github.com/TheAlgorithms/Python.git
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551c65766d
* makes LRUCache constructor concrete * fixes bug in dq_removal in other/least_recently_used + deque.remove() operates by value not index * [mypy] Annotates other/least_recently_used over generic type + clean-up: rename key_reference to match type. * [mypy] updates example to demonstrate LRUCache with complex type * Adds doctest to other/least_recently_used * mypy.ini: Remove exclude = (other/least_recently_used.py) * Various mypy configs * Delete mypy.ini * Add mypy to .pre-commit-config.yaml * mypy --ignore-missing-imports --install-types --non-interactive . * mypy v0.910 * Pillow=8.3.7 * Pillow==8.3.7 * Pillow==8.3.2 * Update .pre-commit-config.yaml * Update requirements.txt * Update pre-commit.yml * --install-types # See mirrors-mypy README.md Co-authored-by: Christian Clauss <cclauss@me.com>
93 lines
2.4 KiB
Python
93 lines
2.4 KiB
Python
from __future__ import annotations
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import sys
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from collections import deque
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from typing import Generic, TypeVar
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T = TypeVar("T")
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class LRUCache(Generic[T]):
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"""
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Page Replacement Algorithm, Least Recently Used (LRU) Caching.
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>>> lru_cache: LRUCache[str | int] = LRUCache(4)
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>>> lru_cache.refer("A")
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>>> lru_cache.refer(2)
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>>> lru_cache.refer(3)
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>>> lru_cache
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LRUCache(4) => [3, 2, 'A']
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>>> lru_cache.refer("A")
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>>> lru_cache
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LRUCache(4) => ['A', 3, 2]
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>>> lru_cache.refer(4)
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>>> lru_cache.refer(5)
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>>> lru_cache
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LRUCache(4) => [5, 4, 'A', 3]
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"""
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dq_store: deque[T] # Cache store of keys
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key_reference: set[T] # References of the keys in cache
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_MAX_CAPACITY: int = 10 # Maximum capacity of cache
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def __init__(self, n: int) -> None:
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"""Creates an empty store and map for the keys.
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The LRUCache is set the size n.
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"""
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self.dq_store = deque()
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self.key_reference = set()
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if not n:
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LRUCache._MAX_CAPACITY = sys.maxsize
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elif n < 0:
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raise ValueError("n should be an integer greater than 0.")
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else:
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LRUCache._MAX_CAPACITY = n
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def refer(self, x: T) -> None:
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"""
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Looks for a page in the cache store and adds reference to the set.
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Remove the least recently used key if the store is full.
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Update store to reflect recent access.
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"""
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if x not in self.key_reference:
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if len(self.dq_store) == LRUCache._MAX_CAPACITY:
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last_element = self.dq_store.pop()
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self.key_reference.remove(last_element)
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else:
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self.dq_store.remove(x)
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self.dq_store.appendleft(x)
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self.key_reference.add(x)
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def display(self) -> None:
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"""
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Prints all the elements in the store.
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"""
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for k in self.dq_store:
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print(k)
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def __repr__(self) -> str:
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return f"LRUCache({self._MAX_CAPACITY}) => {list(self.dq_store)}"
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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lru_cache: LRUCache[str | int] = LRUCache(4)
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lru_cache.refer("A")
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lru_cache.refer(2)
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lru_cache.refer(3)
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lru_cache.refer("A")
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lru_cache.refer(4)
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lru_cache.refer(5)
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lru_cache.display()
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print(lru_cache)
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assert str(lru_cache) == "LRUCache(4) => [5, 4, 'A', 3]"
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