Name of design pattern creating the same object for equal arguments

Question

It's a bit like the singleton pattern with the twist that one passes arguments when acquiring the object and are getting the same object if and only if the arguments are the same. Example in python:

a = get_object(42)
b = get_object(42)
c = get_object(19)

a is b
a is not c

Perhaps you mean memoization?

deceze
– deceze ♦

2024-08-22 13:57:37 +00:00
Commented Aug 22, 2024 at 13:57 — deceze
– deceze ♦, Commented Aug 22, 2024 at 13:57

Guru Stron · Accepted Answer · 2024-08-24 20:04:16Z

0

Function having the following properties:

return values are identical for identical arguments (no variation with local static variables, non-local variables, mutable reference arguments or input streams, i.e., referential transparency)
has no side effects (no mutation of local static variables, non-local variables, mutable reference arguments or input/output streams).

Is called pure. For pure functions you can apply the memoization:

In computing, memoization or memoisation is an optimization technique used primarily to speed up computer programs by storing the results of expensive function calls to pure functions and returning the cached result when the same inputs occur again.

answered Aug 24, 2024 at 20:04

Guru Stron

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Peter Csala · Accepted Answer · 2024-09-02 18:02:14Z

0

In Python memoization is achievable

either via functools.cache:

from functools import cache

@cache
def get_object(id):
   pass

or via functools.lru_cache:

from functools import lru_cache

@lru_cache(maxsize=10)
def get_object(id):
  pass

Please bear in mind, these decorators do not work well with complex data structures like list.

In those cases you would receive an error like this:

TypeError: unhashable type: 'list'

edited Sep 2, 2024 at 18:02

answered Sep 2, 2024 at 15:57

Peter Csala

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