How to make a custom type "true" or not, in Python 1.5.2

Michael Hudson mwh21 at
Mon Feb 19 16:29:42 EST 2001

"Warren Postma" <embed at> writes:

> I am writing a little event object, here is the PyTypeObject declaration:
> Now, how do I make it true or false, it appears that all C Type object
> instances are True, because They Are A Thing, not Nothing, but what if you
> want to make something that can be a Logically False Entity?  Do I have to
> implement the sequence protocol, and implement len(x)?  It doesn't seem that
> it calls my getattr function to check anything. It's just plain true.

You want nb_nonzero in the number methods struct, from memory...  and
the nb_nonzero field from the tp_as_number field from checking the
source (! where does my brain keep all these bits of information?).


  On the other hand,  the following areas are subject to boycott
  in reaction to the rampant impurity of design or execution, as
  determined after a period of study, in no particular order: 

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