Simple Redis Cache Helper in Python

import time
import redis
import json


class SimpleCache:
    def __init__(self, host="localhost", port=6379, db=0, default_ttl=60):
        self.client = redis.Redis(host=host, port=port, db=db, decode_responses=True)
        self.default_ttl = default_ttl

    def get(self, key):
        value = self.client.get(key)
        return json.loads(value) if value else None

    def set(self, key, data, ttl=None):
        self.client.set(key, json.dumps(data), ex=ttl or self.default_ttl)

    def delete(self, key):
        self.client.delete(key)


def fetch_with_cache(cache, key, expensive_function):
    cached = cache.get(key)
    if cached is not None:
        print(f"Cache hit for '{key}'")
        return cached

    print(f"Cache miss for '{key}' — fetching fresh data")
    data = expensive_function(key)
    cache.set(key, data)
    return data


def expensive_lookup(key):
    time.sleep(1)  # simulate slow work
    return {"key": key, "result": f"data for {key}", "computed_at": time.time()}


if __name__ == "__main__":
    cache = SimpleCache(default_ttl=5)
    for _ in range(3):
        result = fetch_with_cache(cache, "user:42", expensive_lookup)
        print(result)
        time.sleep(0.2)
    cache.delete("user:42")