I learned Vue.js and Python/Flask for my side project https://contactcache.com (I didn't want to use Angular or Java/Groovy/Node.js which I knew from previous work).

Vue.js has been an absolute joy to learn and use. Great design & simple ecosystem. Perfect choice for small SPA.

While I like Python in general, on the backend side I think there are also other stacks that'd probably do the job and perhaps do it better. I chose Python since I want to also have a look at data science in the future.