[Numpy-discussion] ndarray.count() ?
robert.kern at gmail.com
Thu Sep 7 15:40:24 CDT 2006
Martin Spacek wrote:
> What's the most straightforward way to count, say, the number of 1s or
> Trues in the array? Or the number of any integer?
> I was surprised to discover recently that there isn't a count() method
> as there is for Python lists. Sorry if this has been discussed already,
> but I'm wondering if there's a reason for its absence.
Mostly, it's simply easy enough to implement yourself. Not all one-liners should
be methods on the array object.
(a == value).sum()
Of course, there are several different things you might do. You might want to
have multiple values broadcast across the array. You might want to reduce the
count along a given axis. You might want to use floating point comparison with a
tolerance. Putting all of those options into one method reduces the convenience
of that method. Putting a crippled implementation (i.e. just that one-liner)
expands the already-enormous API of the ndarray object without much benefit.
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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