| msg318770 - (view) |
Author: Al-Scandar Solstag (solstag) |
Date: 2018-06-05 16:58 |
| Ni! It is not clear at all in the documentation of @lru_cache that the cache takes into account the exact way the function was called, not the values passed to its arguments, as one could/would expect. I mean that for function(a, b, c=3) the three calls below are not considered equivalent as far as the cache is concerned: function(1, 2, 3) function(1, 2, c=3) function(1, 2) I hope this can be clarified in the documentation. I wasted a great deal of time today trying to understand why my calls were not getting cached and only figured it out when I decided to go read @lru_cache's code. It seems very likely that other people have had the same problem. Or worse, people might be using @lru_cache believing it is working when it isn't. Cheers! |
|
|
| msg318774 - (view) |
Author: R. David Murray (r.david.murray) *  |
Date: 2018-06-05 17:25 |
| Agreed that this should be documented. |
|
|
| msg318793 - (view) |
Author: Raymond Hettinger (rhettinger) * |
Date: 2018-06-06 01:07 |
| Sure, I can add a line mentioning that distinct argument patterns may be considered as distinct cache entries even though they otherwise seem to be equivalent calls. That will just be a general statement though. The specific details are implementation dependent, have changed over time, and may change again in the future. |
|
|
| msg318822 - (view) |
Author: Al-Scandar Solstag (solstag) |
Date: 2018-06-06 13:48 |
| Hi Raymond, I think I understand what you mean, and would suggest something along the lines of: """ Note that lru_cache only guarantees cache matches on the exact way function arguments are specified, so the following ways of calling 'def f(a, b=7)' are not guaranteed to cache each other: f(1), f(a=1), f(1, 7), f(1, b=7), f(a=1, b=7). """ |
|
|
| msg320358 - (view) |
Author: Raymond Hettinger (rhettinger) * |
Date: 2018-06-24 06:24 |
| I propose this, "Distinct argument patterns may be considered to be distinct calls with distinct results even if the underlying function sees them as equivalent calls." |
|
|
| msg320422 - (view) |
Author: Al-Scandar Solstag (solstag) |
Date: 2018-06-25 13:28 |
| Speaking frankly, I might not have grasped what might happen by reading your line. I think having at least a minimal example is crucial. Perhaps: "Distinct argument patterns, such as `f(1)` and `f(first_arg=1)`, may not cache for each other even if the underlying function sees them as equivalent calls." |
|
|
| msg320430 - (view) |
Author: Srinivas Reddy Thatiparthy(శ్రీనివాస్ రెడ్డి తాటిపర్తి) (thatiparthy) * |
Date: 2018-06-25 17:06 |
| Hi Raymond, I find your statement hard to understand.I agree with Solstag, it is always helpful to have an example. +1 for solstag wording. |
|
|