list 如何计算Python中零的数量？
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How to count the number of zeros in Python?
提问by derkyzer
My code is currently written as:
我的代码目前写成：
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.
它总是以 25 的形式出现，所以不仅仅是行不包含 0。
回答by Christian
Have you printed rows?
你打印了rows吗？
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.
它是[[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]]，所以你有一个嵌套列表。
If you want to count the number of 0's in those nested lists, you could try:
如果您想计算0这些嵌套列表中's的数量，您可以尝试：
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:
输出：
18
回答by DSM
rowsdoesn't contain any zeroes; it contains lists, not integers.
rows不包含任何零；它包含列表，而不是整数。
>>> 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 listsin rows, you could use a generator expression:
要计算行中任何列表中零的数量，您可以使用生成器表达式：
>>> rows = [[1,2,3],[4,5,6], [0,0,8]]
>>> sum(x == 0 for row in rows for x in row)
2
