Introduction to LRU Cache

LRU (Least Recently Used) cache is a type of cache algorithm that removes the least recently accessed items first. It is useful in scenarios where you want to ensure that the cache contains the most frequently accessed items, which can significantly improve the performance of your application by reducing the time required to fetch data from a slower storage medium.

Key Features and API Usage

Let’s dive into some of the essential APIs provided by LRU cache implementation with code snippets in Python.

1. Initializing the LRU Cache

  
  from cachetools import LRUCache

  # Initialize the cache with a maximum size of 3
  cache = LRUCache(maxsize=3)
  

2. Adding Items to the Cache

  
  # Adding items to the cache
  cache['item1'] = 'A'
  cache['item2'] = 'B'
  cache['item3'] = 'C'
  

3. Accessing Items from the Cache

  
  # Accessing an item
  value = cache['item1']
  print(value)  # Output: A
  

4. Handling Cache Misses

  
  try:
      value = cache['item4']
  except KeyError:
      print("Item not found in cache")
  

5. Updating Existing Items

  
  # Updating an existing item
  cache['item1'] = 'AA'
  

6. Deleting Items from the Cache

  
  # Deleting an item from the cache
  del cache['item2']
  

7. Checking Cache Size

  
  # Checking the number of items in the cache
  size = len(cache)
  print(size)  # Output: 2
  

8. Clearing the Cache

  
  # Clearing all items from the cache
  cache.clear()
  

9. Example Application Using LRU Cache

Here is a simple example of how LRU cache can be implemented in a web application to cache database query results.

  
  from flask import Flask, jsonify
  from cachetools import LRUCache

  app = Flask(__name__)
  cache = LRUCache(maxsize=5)

  def get_data_from_db(key):
      # Simulate a database call
      return {'data': f'Data for {key}'}

  @app.route('/data/')
  def get_data(key):
      if key in cache:
          return jsonify({'cached': True, 'data': cache[key]})
      data = get_data_from_db(key)
      cache[key] = data
      return jsonify({'cached': False, 'data': data})

  if __name__ == '__main__':
      app.run(debug=True)
  

In this example, we use a simple Flask application to serve data that is cached using LRU cache. When a request is made, it first checks if the data is available in the cache before fetching it from the database. This reduces the number of database hits and speeds up response times.

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