How to count the number of zeros in Python?

Question

My code is currently written as:

convert = {0:0,1:1,2:2,3:3,4:0,5:1,6:2,7:1}
rows = [[convert[random.randint(0,7)] for _ in range(5)] for _ in range(5)]
numgood = 25 - rows.count(0)

print numgood
>> 25

It always comes out as 25, so it's not just that rows contains no 0's.

Answer 1

Have you printed rows?

It's [[0, 1, 0, 0, 2], [1, 2, 0, 1, 2], [3, 1, 1, 1, 1], [1, 0, 0, 1, 0], [0, 3, 2, 0, 1]], so you have a nested list there.

If you want to count the number of 0's in those nested lists, you could try:

import random

convert = {0:0, 1:1, 2:2, 3:3, 4:0, 5:1, 6:2, 7:1}
rows = [[convert[random.randint(0, 7)] for _ in range(5)] for _ in range(5)]

numgood = 25 - sum(e.count(0) for e in rows)
print numgood

Output:

18

Answer 2

rows doesn't contain any zeroes; it contains lists, not integers.

>>> row = [1,2,3]
>>> type(row)
<type 'list'>
>>> row.count(2)
1
>>> rows = [[1,2,3],[4,5,6]]
>>> rows.count(2)
0
>>> rows.count([1,2,3])
1

To count the number of zeroes in any of the lists in rows, you could use a generator expression:

>>> rows = [[1,2,3],[4,5,6], [0,0,8]]
>>> sum(x == 0 for row in rows for x in row)
2