Absolutely -- but it's best to put the matter front and center by saying "I've been learning Python, here's a little side project I did" so you don't get slamme

Absolutely -- but it's best to put the matter front and center by saying "I've been learning Python, here's a little side project I did" so you don't get slammed with LC tests or Jeopardy-style phone screens. In fact they might appreciate the fact that you're eager to expand your horizons, especially if you can articulate what you see as limitations in the languages you're currently using.