[Python-ideas] __missing__ object/keyword
tjreedy at udel.edu
Sat Nov 8 21:05:36 CET 2008
Jim Jewett wrote:
> 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:
> And I often catch myself trying to write
> def foo(x, y=object()):
> if y is ... # oops, I need to define the y *outside* the function.
if type(y) is object: ...
And no, there is no problem if a foolish caller passes an object(),
because such has no meaning other than what your sentinal y means.
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