[Tutor] The Boolean operator "and"

[Glen Wheeler]

  Yes...however I was not talking about actual values.  I was talking about
logical expressions.  The chapter in question was on boolean algebra, right?
  Sorry if I unintentionally confused anyone.  Lloyd is also correct.

  Glen

From: "Lloyd Kvam" <pythonTutor at venix.com>
> I think this is better phrasing below.  Those values are equivalent to
> False when used in a context where a boolean would be appropriate.
>
> http://docs.python.org/lib/truth.html#l2h-90
> Lists the values that evaluate as False.
>
> On Fri, 2004-08-06 at 08:47, Lloyd Kvam wrote:
> > x and y can simply be values.  0, 0.0, None, [], '' all evaluate to
>                                                                    ^^as
> > False.
> > >>> x = None
> > >>> y = 0.0
> > >>> result = x and y
> > >>> result
> > >>> print result
> > None
> > >>> print x or y
> > 0.0
> >
> > Note that the values do NOT get changed to booleans.
> >
> >
> > On Fri, 2004-08-06 at 05:10, Glen Wheeler wrote:
> > (snipped)
> >
> > >   Mr Hetland is (of course) correct in his statement you quote above.
The
> > > key part is where he states ``if x is false''.  This is not ``x
evaluates to
> > > False''.
> > >
> > >   A quick interpreter session to hopefully clarify what he is trying
to say:
> > >
> > > >>> x = 3 < 4
> > > >>> x
> > > True
> > > >>> x is True
> > > True
> > > # Note how x actually *is* True
> > > >>> x is False
> > > False
> > > >>>
> > >
> > >   The point is that any logical expression is not stored as a string,
but as
> > > either True or False.  This is neat, since it implies that the
expected
> > > value of any logical expression will be True or False.  Thus, we have
if
> > > statements.
> > >   Any logical statement or expression is evaluated before assignment
to the
> > > variable holding that statement actually occurs.
> > >
> > > >>> x = 1 > 0
> > > >>> y = 1 < 0
> > > >>> x and y
> > > False
> > > >>> x or y
> > > True
> > > >>> x is False
> > > False
> > > >>> x is True
> > > True
> > >
> > >   I hope this helps clear things up.
> > >
> > >   Glen
> > > _______________________________________________
> > > Tutor maillist  -  Tutor at python.org
> > > http://mail.python.org/mailman/listinfo/tutor
> -- 
>
> Lloyd Kvam
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