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

Michael Hudson mwh21 at cam.ac.uk
Mon Feb 19 22:29:42 CET 2001


"Warren Postma" <embed at geocities.com> writes:

> I am writing a little event object, here is the PyTypeObject declaration:
[bobbit]
> 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?).

Cheers,
M.

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