[Numpy-discussion] Issues to fix for 1.7.0rc2.

Benjamin Root ben.root@ou....
Wed Feb 6 08:27:58 CST 2013


On Wed, Feb 6, 2013 at 4:18 AM, Dag Sverre Seljebotn <
d.s.seljebotn@astro.uio.no> wrote:

> On 02/06/2013 08:41 AM, Charles R Harris wrote:
> >
> >
> > On Tue, Feb 5, 2013 at 11:50 PM, Jason Grout
> > <jason-sage@creativetrax.com <mailto:jason-sage@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()
>      ...
>
>
And what if the user passes in a zero or an empty string or an empty list,
or if the return value from get_foo() is a perfectly valid zero?  This is
one of the very few things I have disagreed with PEP8, and Python in
general about.  I can understand implicit casting of numbers to booleans in
order to attract the C/C++ crowd (but I don't have to like it), but what
was so hard about "x is not None" or "len(x) == 0"?

I like my languages explicit.  Less magic, more WYSIWYM.

Cheers!
Ben Root
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