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Groups > comp.lang.python > #64987

Re: 1 > 0 == True -> False

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Jussi Piitulainen wrote:

> Thibault Langlois writes:
> 
>> Hello,
>> 
>> $ python
>> Python 2.7.4 (default, Sep 26 2013, 03:20:26)
>> [GCC 4.7.3] on linux2
>> Type "help", "copyright", "credits" or "license" for more information.
>> >>> 1 > 0 == True
>> False
>> >>> (1 > 0) == True
>> True
>> >>> 1 > (0 == True)
>> True
>> >>>
>> 
>> What am I missing here ?
> 
> One or both of the following:
> 
>    >>> 0 == True
>    False
>    >>> True and False
>    False
>    >>> 1 > 0
>    True
> 
> Or the fact that (1 > 0 == True) means ((1 > 0) and (0 == True)),
> where each expression in such a chain is evaluated once, though in
> this case it really does not matter since 0 is a literal.
> 
> Hm, I don't know if the evaluation short-circuits. I think not, but
> I've never needed to know, and I don't need to know now.

It is easy to check though:

>>> def zero():
...     print("zero")
...     return 0
... 
>>> def one():
...     print("one")
...     return 1
... 
>>> def true():
...     print("true")
...     return True
... 
>>> one() > zero() == true()
one
zero
true
False
>>> zero() > one() == true()
zero
one
False

So yes, evaluation does short-curcuit.

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1 > 0 == True -> False Thibault Langlois <thibault.langlois@gmail.com> - 2014-01-30 03:36 -0800
  Re: 1 > 0 == True -> False Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2014-01-30 12:44 +0100
  Re: 1 > 0 == True -> False Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-01-30 13:46 +0200
    Re: 1 > 0 == True -> False Peter Otten <__peter__@web.de> - 2014-01-30 13:04 +0100
      Re: 1 > 0 == True -> False Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-01-30 14:08 +0200
  Re:1 > 0 == True -> False Dave Angel <davea@davea.name> - 2014-01-30 07:49 -0500
    Re: 1 > 0 == True -> False Thibault Langlois <thibault.langlois@gmail.com> - 2014-01-30 05:40 -0800
      Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 00:55 +1100
      Re: 1 > 0 == True -> False Roy Smith <roy@panix.com> - 2014-01-30 09:08 -0500
        Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 01:18 +1100
          Re: 1 > 0 == True -> False Roy Smith <roy@panix.com> - 2014-01-30 09:49 -0500
            Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 02:02 +1100
        Re: 1 > 0 == True -> False Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-01-30 06:41 -0800
        Re: 1 > 0 == True -> False Thibault Langlois <thibault.langlois@gmail.com> - 2014-01-30 06:46 -0800
          Re: 1 > 0 == True -> False Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-30 17:42 +0000
        Re: 1 > 0 == True -> False Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-01-30 16:56 +0200
          Re: 1 > 0 == True -> False Roy Smith <roy@panix.com> - 2014-01-30 10:46 -0800
            Re: 1 > 0 == True -> False Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-01-30 22:14 +0200
              Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 07:25 +1100
        Re: 1 > 0 == True -> False Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-01-30 15:09 +0000
          Re: 1 > 0 == True -> False Rustom Mody <rustompmody@gmail.com> - 2014-01-30 07:34 -0800
          Re: 1 > 0 == True -> False Roy Smith <roy@panix.com> - 2014-01-30 10:53 -0800
            Re: 1 > 0 == True -> False Rustom Mody <rustompmody@gmail.com> - 2014-01-30 19:33 -0800
          Re: 1 > 0 == True -> False Roy Smith <roy@panix.com> - 2014-01-30 10:56 -0800
            Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 06:03 +1100
              Re: 1 > 0 == True -> False Roy Smith <roy@panix.com> - 2014-01-30 14:09 -0800
                Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 09:29 +1100
            Re: 1 > 0 == True -> False Ethan Furman <ethan@stoneleaf.us> - 2014-01-30 11:22 -0800
            Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 06:48 +1100
    Re: 1 > 0 == True -> False Rotwang <sg552@hotmail.co.uk> - 2014-01-30 19:25 +0000
      Re: 1 > 0 == True -> False Dave Angel <davea@davea.name> - 2014-01-30 15:08 -0500
      Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 07:15 +1100
      Re: 1 > 0 == True -> False Ian Kelly <ian.g.kelly@gmail.com> - 2014-01-30 13:28 -0700
      Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 07:38 +1100
      Re: 1 > 0 == True -> False Ian Kelly <ian.g.kelly@gmail.com> - 2014-01-30 14:17 -0700
      Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 08:31 +1100
      Re: 1 > 0 == True -> False Joshua Landau <joshua@landau.ws> - 2014-01-30 23:36 +0000
        Re: 1 > 0 == True -> False Rotwang <sg552@hotmail.co.uk> - 2014-01-31 00:10 +0000
          Removal of iterable unpacking in function calls (was: 1 > 0 == True -> False) Ben Finney <ben+python@benfinney.id.au> - 2014-01-31 11:21 +1100
            Re: Removal of iterable unpacking in function calls Rotwang <sg552@hotmail.co.uk> - 2014-01-31 00:32 +0000
          Re: 1 > 0 == True -> False Joshua Landau <joshua@landau.ws> - 2014-01-31 00:32 +0000
      Re: 1 > 0 == True -> False Chris Angelico <rosuav@gmail.com> - 2014-01-31 11:01 +1100

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