How to mix maths & text in labels ?

Hi all,
I need to mix maths & text in labels such as title and xlabel.

I first tried the most intuitive way:

  title(r"$x$ and $y$")

but it appeared not to work (don't focus of my silly sample title, the real
one does make sense :wink:

Then I tried

  title(r"$x$ \text{and} $y$")

but I got an error related to the fact that is_string_like() returned False
when passing my title string to it.

Could you please tell me how to achieve it ?

Thanks in advance,