Change cache.add to cache.setdefault

[David Cramer]

Proposal of changing .add to .setdefault before it is adopted. Reason being is consistency.

.add has no clear meaning vs .set
.setdefault is already used for dictionaries
.setdefault clearly states what its doing vs .set

[Malcolm Tredinnick]

Not worth the pain this would cause for everybody using the low-level caching API. "Add" adds a new thing to the cache. The add/set API also corresponds neatly with memcached's API, which is a good idea, since serious caching is going to use memcached and people who are familiar with that shouldn't suddenly have the words changed when looking at a language binding API.

"Setdefault" is a fairly clunky term the way it is used in Python, because it does a lot more than set a default. So using it for other APIs is probably not a good idea.