[Python-ideas] __missing__ object/keyword
veloso at verylowsodium.com
Thu Nov 6 21:47:33 CET 2008
On Thu, Nov 6, 2008 at 3:31 PM, George Sakkis <george.sakkis at gmail.com> wrote:
> Several times I find myself using the following idiom:
> _Missing = object() # sentinel
> def foo(x, y=_Missing):
> if y is _Missing:
> It would be nice if a new object or keyword, say __missing__, was
> introduced as a canonical way to address this common scenario.
> Thoughts ?
This has been proposed and shot down before:
The older proposal didn't give __missing__ the special run-time and
compile-time error behaviors, but this actually just makes things
worse. Why complicate the language merely to save a single idiomatic
line of code dealing with a relatively infrequent use-case?
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