On 02/06/2013 08:41 AM, Charles R Harris wrote:
>
>
> On Tue, Feb 5, 2013 at 11:50 PM, Jason Grout
> <jason-s...@creativetrax.com <mailto:jason-s...@creativetrax.com>> wrote:
>
> On 2/6/13 12:46 AM, Charles R Harris wrote:
> > if we decide to do so
>
> I should mention that we don't really depend on either behavior (we
> probably should have a better doctest testing for an array of None
> values anyway), but we noticed the oddity and thought we ought to
> mention it. So it doesn't matter to us which way the decision goes.
>
>
> More Python craziness
>
> In [6]: print None or 0
> 0
>
> In [7]: print 0 or None
> None
To me this seems natural and is just how Python works? I think the rule
for "or" is simply "evaluate __nonzero__ of left operand, if it is
False, return right operand".
The reason is so that you can use it like this:
x = get_foo() or get_bar() # if get_foo() returns None
# use result of get_bar
or
def f(x=None):
x = x or create_default_x()
...
I guess that after the "a if expr else b" was introduced this has become
less common.
Dag Sverre
>
> Numpy any is consistent with python when considered as logical_or.reduce
>
> In [13]: print array([0, None]).any()
> None
>
> In [14]: print array([None, 0]).any()
> 0
>
> This appears to be an __ror__, __or__ inconsistency in python. Note that
> None possesses neither of those operators.
>
> Chuck
>
>
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