Can py-pde solve a system of differential-algebraic equations?

[jAniceto]

If I have a system of differential-algebraic equations, like:

$$\frac{\partial C}{\partial t} = f_1(C, C_p, \frac{\partial C}{\partial z})$$

$$\frac{\partial C_p}{\partial t} = f_2(C, C_p, \frac{\partial q}{\partial z})$$

$$q = f_3(C_p)$$

Dependent variables are $C$, $C_p$ and $q$. Independent are time, $t$, and position, $z$.

Am I correct that this is not possible to solve in py-pde?

[david-zwicker]

Generally, py-pde cannot solve differential-algebraic equations, but I'm not sure your equation falls under this category. Can't you simply take a derivative w.r.t. to z of the last equation and replace it in the second? In this case, you would be left with only two fields, both described by PDEs. If you need q, you could always re-create it later using the last equation.

[jAniceto]

Yes, in some cases that would be the approach but in others I have actual DAEs. Maybe my example was not the best.
Thanks again.