Count Elements In A List Python

I need to be able to count how many of the string 'O' is in my list top_board = [ [None, None, None, None, None, None, None, None, None], [None, None, None, None, None, No

Solution 1:

cnt = sum([lst.count('O') for lst in top_board])
# then do something depending on cnt

Solution 2:

Try this:

sum(x.count("O") for x in top_board)

Solution 3:

def count_O(l):
    count = 0
    for sublist in l:
        count += sublist.count("O")
    return count


if count_O(top_board) == 0:
    #do something

Solution 4:

if [j for i in top_board for j in i].count('O'):
    print "O is present in the list"

Solution 5:

Update

sum([sum([1 for x in y if x == "O"]) for y in top_board])

(hadn't notice the nesting...)