On Thu, 5 Mar 2020 at 11:30, Lorenzo Monacelli
<[email protected]> wrote:
>
> Dear all,
> I would like to implement some basic manipulation with matrices that I need.
> The problem I'm facing is that I cannot figure out how to recognize correctly
> a MatrixSymbol:
> from sympy.abc import i,j
> A = sy.MatrixSymbol("A",3,3)
> B = sy.MatrixSymbol("B",3,3)
> C = sy.MatrixSymbol("C",3,3)
>
> pippo = A[i,j].subs(A, B+C)
> isinstance(pippo.args[0].args[0].func, sy.MatrixSymbol) # False
> isinstance(B.func, sy.MatrixSymbol) #True
The .func attribute gives MatrixSymbol so you could use:
pippo.args[0].args[0].func is sy.MatrixSymbol
or (note no .func):
isinstance(pippo.args[0].args[0], sy.MatrixSymbol)
> Note, that pippo.args[0].args[0] is B and if you print
> pippo.args[0].args[0].func it returns
> sympy.matrices.expressions.matexpr.MatrixSymbol
>
> So why is it not working?
Because you are asking if MatrixSymbol is an instance of itself:
In [11]: isinstance(MatrixSymbol, MatrixSymbol)
Out[11]: False
--
Oscar
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