isinstance(False, int)
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From: mk on 5 Mar 2010 12:14 >>> isinstance(False, int) True >>> >>> isinstance(True, int) True Huh? >>> >>> issubclass(bool, int) True Huh?! Regards, mk
From: Steve Holden on 5 Mar 2010 13:00 mk wrote: >>>> isinstance(False, int) > True >>>> >>>> isinstance(True, int) > True > > Huh? > >>>> >>>> issubclass(bool, int) > True > > Huh?! > >>> 3+True 4 >>> 3+False 3 >>> Just a brainfart from the BDFL - he decided (around 2.2.3, IIRC) that it would be a good ideal for Booleans to be a subclass of integers. regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 PyCon is coming! Atlanta, Feb 2010 http://us.pycon.org/ Holden Web LLC http://www.holdenweb.com/ UPCOMING EVENTS: http://holdenweb.eventbrite.com/
From: Arnaud Delobelle on 5 Mar 2010 13:03 mk <mrkafk(a)gmail.com> writes: >>>> isinstance(False, int) > True >>>> >>>> isinstance(True, int) > True > > Huh? > >>>> >>>> issubclass(bool, int) > True > > Huh?! > > Regards, > mk Yes, and: >>> True + False 1 In fact: >>> 1 == True True >>> 0 == False True So what's your question? -- Arnaud
From: Steven D'Aprano on 5 Mar 2010 13:07 On Fri, 05 Mar 2010 18:14:16 +0100, mk wrote: >>>> isinstance(False, int) > True > >>> > >>> isinstance(True, int) > True > > Huh? Yes. Do you have an actual question? > >>> issubclass(bool, int) > True > > Huh?! Exactly. Bools are a late-comer to Python. For historical and implementation reasons, they are a subclass of int, because it was normal for people to use 0 and 1 as boolean flags, and so making False == 0 and True == 1 was the least likely to break code. E.g. back in the day, you would have something like: {2:None}.has_key(2) -> 1 So folks would do: print "The key is", ["missing", "present"][d.has_key(key)] Which still works even now that has_key returns True or False rather than 1 or 0. -- Steven
From: Rolando Espinoza La Fuente on 5 Mar 2010 13:27
On Fri, Mar 5, 2010 at 2:00 PM, Steve Holden <steve(a)holdenweb.com> wrote: [...] > > Just a brainfart from the BDFL - he decided (around 2.2.3, IIRC) that it > would be a good ideal for Booleans to be a subclass of integers. > I would never figured out >>> bool.__bases__ (<type 'int'>,) Doesn't have side effects not knowing that False/True are ints? Regards, Rolando |