What values are considered false?

[Bernhard Herzog]

scarblac at pino.selwerd.nl (Remco Gerlich) writes:

> Jason <caljason76 at yahoo.com> wrote in comp.lang.python:
> > In my experimentation 0, None, "", [], and () all seem to be
> > considered false.  Just to confound me none of them are == to each
> > other.  Coming from a Scheme world this is confusing.  Are there any
> > other values that are false?
> 
> {}, at least. Any classes that return the right results on certain special
> functions (__nonzero__(), if I remember correctly).

or __len__ if __nonzero__ isn't defined.

> > Why aren't () and "" the same thing?
> 
> Because one is an empty tuple and one is an empty string.

Plus they're not equal or identical in scheme either, at least not in
guile:

guile> (equal? "" ())
#f
guile> (eq? "" ())
#f


   Bernhard

-- 
Intevation GmbH                                 http://intevation.de/
Sketch                                 http://sketch.sourceforge.net/
MapIt!                                               http://mapit.de/