Counting 2d lists in python

Question

How can I count the number of items that are 'hit' in this 2d list??

grid = [['hit','miss','miss','hit','miss'],
     ['miss','miss','hit','hit','miss'],
     ['miss','miss','miss','hit','hit'],
     ['miss','miss','miss','hit','miss'],
     ['hit','miss','miss','miss','miss']]

battleships = 0
for i in grid:
    if i == "hit":
    battleships = battleships + 1
print battleships

I know that code is wrong, but it gives an idea of what I want to do I hope??

thanks

Solution 1

Use list.count:

>>> ['hit','miss','miss','hit','miss'].count('hit')
2

>>> grid = [['hit','miss','miss','hit','miss'],
...      ['miss','miss','hit','hit','miss'],
...      ['miss','miss','miss','hit','hit'],
...      ['miss','miss','miss','hit','miss'],
...      ['hit','miss','miss','miss','miss']]
>>> [row.count('hit') for row in grid]
[2, 2, 2, 1, 1]

And sum:

>>> sum(row.count('hit') for row in grid)
8

Solution 2

If I had code that used 2D lists quite a bit, I would make a generator that returns each element in a 2D list:

def all_elements_2d(l):
    for sublist in l:
        for element in sublist:
            yield element

And then you can do other things with it, like count all the 'hit' strings:

hits = sum(element == 'hit' for element in all_elements_2d(grid))

Comments

[user2212774]

can you explain why [row.count('hit') for row in grid] is within brackets? also, how is this counting within the nested lists? i.e., if I wrote print grid.count("hit"), why doesn't that count through all the lists? I know I can write something like grid[1].count which will count within the second list, but how is your code accessing the contents of all the nested lists?

[falsetru]

@user2212774, It's list comprehension. 'list.count' does not search nested list. It only match its items.

[Kristijan Iliev]

you should explain the code, add some text along with it, not just post it like that.