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

if i == "hit": is wrong, i is a list

Grijesh Chauhan
– Grijesh Chauhan

2014-02-12 09:14:00 +00:00
Commented Feb 12, 2014 at 9:14 — Grijesh Chauhan
– Grijesh Chauhan, Commented Feb 12, 2014 at 9:14

falsetru · Accepted Answer · 2014-02-12 09:12:47Z

23

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

answered Feb 12, 2014 at 9:12

falsetru

371k69 gold badges769 silver badges659 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user2212774 Over a year ago

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 Over a year ago

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

RemcoGerlich · Accepted Answer · 2014-02-12 09:22:08Z

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))

answered Feb 12, 2014 at 9:22

RemcoGerlich

31.4k6 gold badges66 silver badges83 bronze badges

Comments

Shubham Doshi · Accepted Answer · 2015-07-20 07:10:33Z

0

Transaction=[['Mango','Onion','Jar','Key-chain','Eggs','Chocolates'],
['Nuts','Onion','Jar','Key-chain','Eggs','Chocolates'],
['Mango','Apple','Key-chain','Eggs'],
['Mango','Toothbrush','corn','Key-chain','Chocolates'],
['corn','Onion','Key-chain','Knife','Chocolates']
]
count1=[['Mango',0],['Onion',0],['Jar',0],['Key-chain',0],['Eggs',0],
['Chocolates',0],['Nuts',0],['Apple',0],['Toothbrush',0],['corn',0],['Knife',0]]
for j in range(0,10):
 x=0
for i in range(0,5):
 x=x+Transaction[i].count(count1[j][0]);
count1[j][1]=x
print count1

answered Jul 20, 2015 at 7:10

Shubham Doshi

1

1 Comment

Kristijan Iliev Over a year ago

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

Collectives™ on Stack Overflow

Counting 2d lists in python

3 Answers 3

2 Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related