# Are there some notions of distance between two policies?

I want to determine some distance between two policies $$\pi_1 (a \mid s)$$ and $$\pi_2 (a \mid s)$$, i.e. something like $$\vert \vert \pi_1 (a \mid s) - \pi_2(a \mid s) \vert \vert$$, where $$\pi_i (a\mid s)$$ is the vector $$(\pi_i (a_1 \mid s), \dots, \pi_i(a_n \mid s))$$. I am looking for a sensible notion for such a distance.

Are there some standard norms/metrics used in the literature for determining a distance between policies?