@lru_cache on functions with no arguments

[Paul Moore]

On Tuesday, 1 August 2017 00:31:52 UTC+1, t... at tomforb.es  wrote:
> Am I right in thinking that using `maxsize=None` is best for functions that accept no arguments? Should we even be using a `lru_cache` in such situations, or write our own simple cache decorator instead?

It seems like overkill to use lru_cache for this case - it's designed to map arguments to results, so it makes little sense when there are no arguments. It's also got LRU arglist management and thread safety overheads, so there's a lot of unneeded overhead for this usage.

_sentinel = object()
_val = _sentinel
def val():
    if _val is _sentinel:
        # Calculate _val
    return _val

seems entirely sufficient for this case. Write a custom decorator if you use the idiom often enough to make it worth the effort.

Paul