create mock device class

.gitignore

 # ignore any virtual environment
 *venv
+
+# ignore pycache
+*__pycache__
\ No newline at end of file

README.md

 # README
 
-# First create a python virtual environment
+## First create a python virtual environment
 
 ```bash
 python3 -m venv demo_venv
@@ -17,4 +17,11 @@ which pip
 $ ~/tiqi-js-tutorial/demo_venv/bin/pip
 which python
 $ ~/tiqi-js-tutorial/demo_venv/bin/python
+```
+
+## Create mock device class
+
+```bash
+mkdir device
+touch device/__init__.py
 ```
\ No newline at end of file

device/__init__.py

+from .device import Device

device/device.py

+class Device:
+    __voltage = 0.0
+    __current = 0.0
+
+    def __init__(self):
+        # code to connect to device
+        self.__voltage = 1.0
+        self.__current = 0.0
+
+    def _get_voltage(self):
+        # read voltage from device
+        voltage = self.__voltage
+        return voltage
+
+    def _set_voltage(self, new_voltage):
+        # write voltage to device
+        self.__voltage = new_voltage
+
+    def _get_current(self):
+        # read current from device
+        current = self.__curent
+        return current
+
+    def _set_current(self, new_current):
+        # write current to device
+        self.__curent = new_current
+
+    def _calculate_resistance(self):
+        current = self._get_current()
+        voltage = self._get_voltage()
+        resistance = voltage / current
+        return resistance