[Python-ideas] __missing__ object/keyword
tjreedy at udel.edu
Sat Nov 8 21:19:50 CET 2008
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.
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