Re: [Python-ideas] __missing__ object/keyword

Bruce Leban wrote:

The problem with using a value like None as some have proposed is that None may be a valid parameter value.

It usually is not, and when it is, a private object suffices.

Thus the only safe value is a special value like a throwaway object.

Yes, a private instance of object().

There *is* one guaranteed way of ensuring that I can't use a variable's value: leaving it unbound.

This Perl, etc. concept does not fit Python's name-object model. A Python mappings and sequences cannot have a key or index without a value. To propose otherwise is a major conceptual change. tjr