The rule is pretty simple: if you list a language or a tool on your resume, you should be prepared to answer questions about it during your interview. If you claim to know Python, and I ask you a very basic Python question that you can't answer, it's going to be embarrassing, and will probably work against you.
As long as you are comfortable talking about the skills and your competency in a face to face interview, I would throw it on there. If the employer is interested in the skills, they will likely bring it up during the interview.
However, make sure that what you put on there is relevant to the job you are applying for. No point throwing C++ in if you are applying for a job that is solely based on Python, but feel free to add them if they could be related e.g. You code in Java mentioning CSS or HTML doesn't hurt for a web developer role.