TTL Memoized - A memoized decorator with TTL (time-to-live) support.

The idea of memoized is great, as some resources are expensive, so you want to cache them.

However, there isn't a memoized lib support TTL (time-to-live) at the moment, or I haven't find any thing yet.

So I implement this ttl_memoized to fill in the gap here.

Also, this lib is meant to be thread-safe, using threading.local object to store the variables.

Installation:

Should be faily simple using pip:

pip install ttl_memoized

Usage

The usage is simple, and the best way to explain it, is with my test cases:

def test_basic():

  @memoized(ttl=0.5)
  def a(name):
    return datetime.datetime.now()

  @memoized(ttl=0.5)
  def b(name, *args, **kwargs):
    return datetime.datetime.now()

  a1 = a(1)
  b1 = b(1, 2, 3, what='ever', you='want', to='be')

  for i in range(100):
    assert a1 == a(1)

  for i in range(100):
    assert b1 is b(1, 2, 3, what='ever', you='want', to='be')

  a2 = a(2)
  assert a2 != a1

  # let the cache expired...
  time.sleep(0.51)

  assert a(1) != a1
  assert b1 != b(1, 2, 3, what='ever', you='want', to='be')

Ceveat

The parameter for the functions is required to be serializable with json libs, as the lib is using json to build the keys from parameters.