How to include external Jar in python

I have a 3rd party jar (cal.jar) which has simple addition, substraction methods under Calculator.java. In python I would like to use that addition, substraction methods. I have referred many resources but nothing worked. I tried https://www.datasciencelearner.com/how-to-call-jar-file-using-python/ I tried jpype(https://code-maven.com/calling-java-from-python) and py4j but I am using python 3.6.X which don't have support of jpype. From py4j I didn't get way to add external jar. I am using python 3.6 and java 1.8.