Re: weird behaviour of "0 in [] is False"

[John Roth]

"Paul Robson" <[EMAIL PROTECTED]> wrote in 
message news:[EMAIL PROTECTED]
Sylvain Thenault wrote:
l = []
0 in (l is False)
(l is False) is not a tuple or list, it's a boolean value.
Traceback (most recent call last):
File "<stdin>", line 1, in ?
TypeError: iterable argument required
(0 in l) is False
True
0 in l is False becuase l is empty, so it's False is False which is true,
(except in Intercal probably and Visual C++)
0 in l is False
False
l is False is False because l is not the value false though it has a false
value (err.....)
Okay.
l != False because it's not the displayed value false
but if not l would evaluated to true because [] is a false equivalent.
0 in False .... okay.... this should be an error ..... something to do 
with
the equivalence confusion of what False is ?
It's not an error. As one of the first responders said, check
the language definition. That defines both 'in' and 'is'
as equality operators, and defines exactly what a chain
of equality operators means.
In this case, it means:
(0 in l) and (l is False)
The and short circuits, giving the result of False without
ever doing the final comparison.
Granted, that's not exactly obvious...
John Roth



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