擅长:python、mysql、java
<pre><code>a = np.random.random_integers(-1, 1, (10,3))
>>> a
array([[ 0, 0, -1],
[ 1, -1, -1],
[ 0, 1, 1],
[-1, 0, 0],
[ 1, -1, 0],
[-1, 1, 1],
[ 0, 1, 0],
[ 1, -1, 0],
[-1, 0, 1],
[ 1, -1, 1]])
>>>
</code></pre>
<p>您可以在任何维度上对numpy数组进行切片。前七行是:</p>
^{pr2}$
<p>在数组上迭代生成可以求和的行。布尔索引可用于根据条件选择项:</p>
<pre><code>>>> for row in a[:7,:]:
... less_than_zero = row[row < 0]
... sum_less_than = np.sum(less_than_zero)
... print('row:{:<14}\tless than zero:{:<11}\tsum:{}'.format(row, less_than_zero, sum_less_than))
row:[ 0 0 -1] less than zero:[-1] sum:-1
row:[ 1 -1 -1] less than zero:[-1 -1] sum:-2
row:[0 1 1] less than zero:[] sum:0
row:[-1 0 0] less than zero:[-1] sum:-1
row:[ 1 -1 0] less than zero:[-1] sum:-1
row:[-1 1 1] less than zero:[-1] sum:-1
row:[0 1 0] less than zero:[] sum:0
>>>
</code></pre>