[Numpy-discussion] What is an empty matrix ?

David Cournapeau david at ar.media.kyoto-u.ac.jp
Wed Jul 4 07:39:13 EDT 2007

Nils Wagner wrote:
> David Cournapeau wrote:
>> Hi,
>>     I was wondering what an empty matrix is, and what it is useful for 
>> (by empty matrix, I mean something created by numpy.matrix([])) ? Using 
>> those crash some functions (see for example scipy ticket #381), and I am 
>> not sure how to fix this bug.
>>     David
>> _______________________________________________
>> Numpy-discussion mailing list
>> Numpy-discussion at scipy.org
>> http://projects.scipy.org/mailman/listinfo/numpy-discussion
> empty(...)
>     empty((d1,...,dn),dtype=float,order='C')
>     Return a new array of shape (d1,...,dn) and given type with all its
>     entries uninitialized. This can be faster than zeros.
I understand numpy.empty, but this is different: an empty matrix is not 
equivalent at all to empty. What I am talking about is what is the 
nature of something lie numpy.array((1, 0)) ? I am actually wondering 
whether it makes sense at all.

a = numpy.matrix([])
b = a + 1

does not raise any error, but I don't see how this should be considered 
meaningful ?


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