How to measure voltage and current in pyspice

hi,everybody!

I’ve built a memristor model in Pspice,The model can run .I wanted it to run in pyspice, but there was an error.

In PSpice, the following statement is OK :
Emem plus aux value={-I(Emem)V(x)(1000-10)}

But in pyspice,An error occurred.

NameError: name ‘V’ is not defined

The reason is that V (x) and I (EMEM) have problems.How can I solve this problem?

Thank you very much!

Environment (windows10, Python 3.2, PySpice 1.4.3, NGspice)

Expected Behaviour

Actual Behaviour

Steps to reproduce the behaviour

@ fsalvaire