How to check if I did damage last turn?

I would like to see if I did damage to enemy in that action phase.
Is there any in-game function to find this information?
Or can I get enemy’s health last turn so that I can compare to the health remaining this turn.

You can save game_state from previous turn just before u end the turn, in the next turn u can comapre it with the actual game_state.

Ermm…Can you explain briefly how can I do that?

the easiest way would be:
at start of the game create global list variable game_state_history = []
and at the end of every turn u can just game_state_history .append(game_state)

now u can compare hp this turn to provious using:
game_state_history[-1].enemy_health - game_state.enemy_health

why did you use [-1]?

[-1] returns the last item in a list, ie the most recent item you added.

This is standard python syntax, please try and google syntax things before asking as there are tons of resources available to help understand these things.