We don't know what your skills and interests are.
I have a degree in Electrical Engineering. Wouldn't it have been better if I got a law degree? No, I had no interest in being a lawyer.
Aside from that, what do you mean by a "certificate". In general, certificates are not worth much at all.
I will also add that it *might* be easier to learn a language on your own but Data Science might be better learned in a classroom. That's because you can clearly see the output of a computer program.
So, if you have a certificate in Data Science, it's something to put on your resume, but you can add that you studied Python on your own.
Keep in mind that a resume is ONLY to get you an interview -- not a job. At the interview, you will have an opportunity to sell yourself. THAT is what gets you a job.