How to measure voltage and current in pyspice

[huszing]

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

[huszing]

thanks