"0 in [True,False]" returns True

[bonono at gmail.com]

Antoon Pardon wrote:
> Op 2005-12-12, Fredrik Lundh schreef <fredrik at pythonware.com>:
> > Pierre Quentel wrote:
> >
> >> In some program I was testing if a variable was a boolean, with this
> >> test : if v in [True,False]
> >>
> >> My script didn't work in some cases and I eventually found that for v =
> >> 0 the test returned True
> >>
> >> So I changed my test for the obvious "if type(v) is bool", but I still
> >> find it confusing that "0 in [True,False]" returns True
> >>
> >> By the way, I searched in the documentation what "obj in list" meant and
> >> couldn't find a precise definition (does it test for equality or
> >> identity with one of the values in list ? equality, it seems) ; did I
> >> miss something ?
> >
> >>>> issubclass(bool, int)
> > True
> >>>> isinstance(False, int)
> > True
> >>>> False == 0
> > True
> >>>> int(False)
> > 0
> >
> > but seriously, unless you're writing an introspection tool, testing for
> > bool is pretty silly.  just use "if v" or "if not v", and leave the rest to
> > Python.
>
> That depends on the circumstances. I have code where a particular
> variable can be a boolean or an integer. I don't want that code
> to behave the same on 0 and False nor on any other number and
> True.
>
Then your program/implementation/requirement is wrong because it
doesn't fit in the use case of "if v:" or "if not v:", refactor  ;-)