core.py 文件源码

def __new__(cls, lhs, rhs, strict=False, status=None, like=None):
        cls._strict = strict
        if strict:
            lhs = sympify(lhs)
            rhs = sympify(rhs)
            # Tuple of things that can be on the lhs of an assignment
            assignable = (Symbol, MatrixSymbol, MatrixElement, Indexed, Idx)
            #if not isinstance(lhs, assignable):
            #    raise TypeError("Cannot assign to lhs of type %s." % type(lhs))
            # Indexed types implement shape, but don't define it until later. This
            # causes issues in assignment validation. For now, matrices are defined
            # as anything with a shape that is not an Indexed
            lhs_is_mat = hasattr(lhs, 'shape') and not isinstance(lhs, Indexed)
            rhs_is_mat = hasattr(rhs, 'shape') and not isinstance(rhs, Indexed)
            # If lhs and rhs have same structure, then this assignment is ok
            if lhs_is_mat:
                if not rhs_is_mat:
                    raise ValueError("Cannot assign a scalar to a matrix.")
                elif lhs.shape != rhs.shape:
                    raise ValueError("Dimensions of lhs and rhs don't align.")
            elif rhs_is_mat and not lhs_is_mat:
                raise ValueError("Cannot assign a matrix to a scalar.")
        return Basic.__new__(cls, lhs, rhs, status, like)