error while defining variables with units and expression

[CorOscar]

Hello,
When defining a variable from class BaseVariable with an expression, there is a conflict between the assigned units and the derived one from the expression. See the screenshot attached.
Regards,
Oscar

[schymans]

Thanks for reporting, @CorOscar. I admit that the error message is a bit useless here, we need to clear this up. But your example is a bit convoluted, so I am not sure how to find the underlying problem. We have never envisaged the definition of internal variables within the definition of variables, that was only meant for the definition of equations. The idea of internal variables was to avoid the use of e.g. 1.01 in an expression, as you still do in iv_T above. I would first define T, T_kv and iv_T as variables and then an equation:

class eq_Tkv(Equation):
    """Empirical equation"""
    class c1(Variable):
        """Internal variable""""
        default = 1.01
    expr = Eq(T_kv, c1 * (T + iv_T))

If you still have a problem with this, could you provide a link to your code or a complete code snippet that I could copy and paste to check what is wrong?