擅长:python、mysql、java
<p>对于大型数组,此解决方案应该更有效(它迭代可能的索引值,而不是<code>i</code>的单个项):</p>
<pre><code>import numpy as np
i = np.array([0,0,1,2,2])
d = np.array([0,1,2,3,4])
i_max = i.max()
c = np.empty(i_max+1)
for j in range(i_max+1):
c[j] = d[i==j].sum()
print c
[1. 2. 7.]
</code></pre>