[Python-ideas] dict.setdefault_call(), or API variations thereupon

[Michael Selik]

On Fri, Nov 2, 2018 at 5:25 PM Anders Hovmöller <boxed at killingar.net> wrote:

> Could you explain what the difference is between defaultdicts "factory
> which is unconditionally called when the key is missing" and "the default
> is evaluated only on need"?
>

The distinction was the motivation for this thread: setdefault requires a
constructed default instance as an argument, regardless of whether the key
is missing, whereas defaultdict's factory is only called if necessary. If
the key is present in a defaultdict, no default is constructed.
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