擅长:python、mysql、java
<pre><code>import numpy as np
r1 = np.array([[11, 15],
[15, 15],
[14, 14]])
equal_to_15 = (r1[:,0] == 15) & (r1[:,1] == 15)
less_than_15 = (r1[:,0] < 15) & (r1[:,1] < 15)
</code></pre>
<p>结果:</p>
^{pr2}$
<p>错误消息:</p>
<p>当你比较一个数组和整数时,你得到一个布尔数组。在</p>
<pre><code>>>> np.array([13, 15]) == 15
array([False, True], dtype=bool)
>>> if _:
... print 'Hi'
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
</code></pre>
<p>numpy不会评估整个数组的真实性,但是如果我们这样做了:</p>
<pre><code>>>> if (np.array([13, 15]) == 15).any():
... print 'Hi'
...
Hi
</code></pre>