Adam Groszer wrote at 2006-11-17 13:13 +0100:
>What is the `good` behaviour regarding None values?
>Do we need to catalog them or skip them?

If you index them, you rely on a non garanteed implementation artefact:

  Python explicitly does not garanteed that comparisons between
  objects of different type are persistent across restarts.

  The BTree variants used in the implementation of indexes
  require that the keys are persistenty compared.
  Failing to do so, will break the index.

  The current Python implementation ensures persistent comparison
  results. Thus, you are on the good side.

  However, earlier Python implementations did not and maybe
  future implementations may not, too....

It is safer, to have just a single key type in your indexes...

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