[Numpy-discussion] New Operators in Python

Colin J. Williams cjw@sympatico...
Sun Mar 25 09:12:54 CDT 2007

Charles R Harris wrote:
> On 3/24/07, *Travis Oliphant* <oliphant@ee.byu.edu 
> <mailto:oliphant@ee.byu.edu>> wrote:
>     Every so often the idea of new operators comes up because of the need to
>     do both "matrix-multiplication" and element-by-element multiplication.
>     I think this is one area where the current Python approach is not as
>     nice because we have a limited set of operators to work with.
>     One thing I wonder is if we are being vocal enough with the Python 3000
>     crowd to try and get additional operators into the language itself.
>     What if we could get a few new operators into the language to help us.
>     If we don't ask for it, it certainly won't happen.
>     My experience is that the difficulty of using the '*' operator for both
>     matrix multiplication and element-by-element multiplication
>     depending on
>     the class of the object is not especially robust.  It makes it harder to
>     write generic code, and we still haven't gotten everything completely
>     right.
>     It is somewhat workable as it stands, but I think it would be nicer if
>     we could have some "meta" operator that allowed an alternative
>     definition of major operators.   Something like @*  for example (just
>     picking a character that is already used for decorators).
> Yes indeed, this is an old complaint. Just having an infix operator 
> would be an improvement:
> A dot B dot C
> Not that I am suggesting dot in this regard ;) In particular, it 
> wouldn't parse without spaces. What about division? Matlab has both / 
> and \ for left and right matrix division and something like that could 
> call solve instead of inverse, leading to some efficiencies. 

Yes, thanks to a suggestion from Alan Isaac, this was implemented in 
PyMatrix (based on numarray and not yet converted to numpy). / served 
for one and // for the other.

Regarding an additional multiply operator, I don't see the need for it. 
   A matrix and and array are similar dut different animals.

Colin W.

We also
> have both dot and tensordot, which raises the problem of interpretation 
> when ndim > 2.
> Chuck
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