Replace python is_A to isinstance(*, A)

[latot]

Hi, well, some times octave/octsympy/python send weird things, and i think this can help to normalize part of this, its when for some reason octsympy try do something like this Matrix().is_Symbol, sadly i don't know how reproduce it, only happen, or want a way to reproduce it?

Thx. Cya.

[cbm755]

hmmm, None is an annoying special case where calling is_Symbol is an error, because S(None) is just None and not a Sympy object.

Could be a good to have a concrete example.

Maybe something like solve with equations where Sympy cannot find a solution. IIRC, that gives a less-than-ideal error message, possibly related.