philiprehberger-cache-kit 0.4.0

Lightweight in-memory cache with TTL, LRU eviction, and tag-based invalidation

philiprehberger-cache-kit

Lightweight in-memory cache with TTL, LRU eviction, and tag-based invalidation.

Installation

pip install philiprehberger-cache-kit

Usage

Basic Cache

from philiprehberger_cache_kit import Cache

cache: Cache[str] = Cache(max_size=1000)

cache.set("key", "value")
print(cache.get("key"))  # "value"

TTL (Time-to-Live)

cache = Cache(default_ttl=60.0)  # 60 seconds default

cache.set("session", "abc123")           # uses default TTL
cache.set("temp", "data", ttl=5.0)       # expires in 5 seconds
cache.set("permanent", "data", ttl=None) # no expiry when default is set

LRU Eviction

cache = Cache(max_size=100)

# When full, least recently used entries are evicted first
# Expired entries are evicted before non-expired ones
for i in range(200):
    cache.set(f"key-{i}", f"value-{i}")

print(cache.size)  # 100

Tag-Based Invalidation

cache.set("user:1", user_data, tags={"users", "team-a"})
cache.set("user:2", user_data, tags={"users", "team-b"})
cache.set("post:1", post_data, tags={"posts", "team-a"})

# Invalidate all entries tagged "team-a"
removed = cache.invalidate_by_tag("team-a")
print(removed)  # 2

Lazy load with get_or_compute

from philiprehberger_cache_kit import Cache

cache: Cache[dict] = Cache(max_size=1000)

def fetch_user(user_id: int) -> dict:
    # Expensive lookup (DB, HTTP, etc.) — only called on cache miss.
    return {"id": user_id, "name": "Ada"}

# First call: computes, caches with TTL/tags, returns the value (miss).
user = cache.get_or_compute(
    "user:1",
    lambda: fetch_user(1),
    ttl=60.0,
    tags=["users"],
)

# Second call within TTL: returns cached value, compute_fn is NOT invoked (hit).
user = cache.get_or_compute("user:1", lambda: fetch_user(1))

Batch Operations

# Set multiple entries at once
cache.set_many({"a": 1, "b": 2, "c": 3}, ttl=30.0)

# Get multiple entries at once (skips missing/expired)
results = cache.get_many(["a", "b", "missing"])
print(results)  # {"a": 1, "b": 2}

Cache Statistics

from philiprehberger_cache_kit import Cache, CacheStats

cache: Cache[str] = Cache(max_size=100)

cache.set("x", "hello")
cache.get("x")        # hit
cache.get("missing")  # miss

stats = cache.stats()
print(stats.hits)      # 1
print(stats.misses)    # 1
print(stats.hit_rate)  # 0.5
print(stats.evictions) # 0
print(stats.expired)   # 0

cache.reset_stats()    # zero out all counters

Other Operations

cache.has("key")        # check existence
"key" in cache          # same as has()
cache.delete("key")     # delete single entry
cache.keys()            # list all non-expired keys
len(cache)              # count of non-expired entries
cache.get_entry("key")  # get CacheEntry with tags, expires_at
cache.clear()           # remove everything

API

Function / Class	Description
Cache(max_size=1000, default_ttl=None)	Create a new cache
.set(key, value, ttl=None, tags=None)	Store a value
.get(key, default=None)	Retrieve a value
.get_or_compute(key, compute_fn, ttl=None, tags=None)	Return cached value, or compute and cache it on miss
.get_many(keys)	Retrieve multiple values, skip missing/expired
.set_many(items, ttl=None)	Store multiple values
.has(key)	Check if key exists and is not expired
.delete(key)	Remove a key
.invalidate_by_tag(tag)	Remove all entries with a tag
.clear()	Remove all entries
.keys()	List non-expired keys
.get_entry(key)	Get CacheEntry object (value, expires_at, tags)
.stats()	Get CacheStats (hits, misses, evictions, expired, hit_rate)
.reset_stats()	Zero out all stat counters
.size	Number of stored entries
len(cache)	Number of non-expired entries
key in cache	Check key existence
CacheStats	Dataclass with hits, misses, evictions, expired, hit_rate

Development

pip install -e .
python -m pytest tests/ -v

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License

MIT