07.01.18 22:33, Chris Angelico пише:
On Mon, Jan 8, 2018 at 7:13 AM, Thomas Jollans <t...@tjol.eu> wrote:
On 07/01/18 20:55, Chris Angelico wrote:
Under what circumstances would you want "x != y" to be different from
"not (x == y)" ?
In numpy, __eq__ and __ne__ do not, in general, return bools.
a = np.array([1,2,3,4])
b = np.array([0,2,0,4])
a == b
array([False, True, False, True], dtype=bool)
a != b
array([ True, False, True, False], dtype=bool)
Thanks, that's the kind of example I was looking for. Though numpy
doesn't drive the core language development much, so the obvious next
question is: was this why __ne__ was implemented, or was there some
other reason? This example shows how it can be useful, but not why it
exists.
AFAIK this was the main reason. This can be also used for creating queries.
NumPy inspired 4 or 5 core features which are rarely used outside of
NumPy. They include the possibility of comparison operators to return
non-booleans.
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