Antoon Pardon wrote: > Op 2005-12-12, Fredrik Lundh schreef <[EMAIL PROTECTED]>: > > 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 ;-)
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