How can I efficiently save a list of random numbers in sets of 3, which i will later be able to access? --Python

I have a 3d list to which I am randomly appending the string 'baddie' n number of times - in this case n = 20. I am appending randomly by generating 3 random ints which are used as the indexes to which I am appending to. What i would like is to be able to save these random sets of indexes so I can later manipulate them in my code. I was thinking I could possibly save them to a separate list as the 'for loop' iterates through generating the random values.

    class board_works():
        def __init__(self):
            self.a = 2
            self.b = 3
            self.c = 5

            self.board = [[[ [] for _ in range(self.a)]
                         for _ in range(self.b)]
                         for _ in range(self.c)]


        def enemy_set(self):
            n = 20
            for count in range(0,n):
                 randa= random.randint(0,self.a-1)
                 randb= random.randint(0,self.b-1)
                 randc= random.randint(0,self.c-1)
                 self.board[randc][randb][randa].append('baddie') 
                 n = n - 1
                 if n == 0:
                     print(self.board)