title: Numpy : The truth value of an array with more than one element is ambiguous
body: <p>I am really confused on why this error is showing up. Here is my code:</p>
  
  <pre><code>import numpy as np
  
  x = np.array([0, 0])
  y = np.array([10, 10])
  a = np.array([1, 6])
  b = np.array([3, 7])
  points = [x, y, a, b]
  max_pair = [x, y]
  other_pairs = [p for p in points if p not in max_pair]
  &gt;&gt;&gt;ValueError: The truth value of an array with more than one element is ambiguous. 
  Use a.any() or a.all()
  (a not in max_paix)
  &gt;&gt;&gt;ValueError: The truth ...
  </code></pre>
  
  <p>What confuses me is that the following works fine:</p>
  
  <pre><code>points = [[1, 2], [3, 4], [5, 7]]
  max_pair = [[1, 2], [5, 6]]
  other_pairs = [p for p in points if p not in max_pair]
  &gt;&gt;&gt;[[3, 4], [5, 7]]
  ([5, 6] not in max_pair)
  &gt;&gt;&gt;False
  </code></pre>
  
  <p>Why is this happening when using numpy arrays? Is <code>not in/in</code> ambiguous for existance?<br>
  What is the correct syntax using <code>any()\all()</code>?</p>