title: matplotlib plot a numpy array as many lines with a single label
body: <p>I have a list of list of data to plot as many lines. Basically:
  [dataset1, dataset2].
  But the point is that I want to put a single label in common to all these lines.
  Here is an example:</p>
  <pre class="lang-py prettyprint-override"><code>data = np.array([[1, 2, 3, 4, 5, 6], [1, 5, 3, 8, 9, 6]])
  plt.plot(np.transpose(data), c = &quot;b&quot;, label=&quot;hello stack&quot;)
  plt.legend()
  plt.show()
  </code></pre>
  <p><a href="https://i.stack.imgur.com/tu7vY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tu7vY.png" alt="enter image description here" /></a></p>
  <p>A way to do that can be to convert the numpy array into a list of list, then iterate through each datasets too plot them separately, and giving a label to the first one only.
  But in order to have a more fancy code and for my personal curiosity, I'm looking for a way to do it by plotting the numpy array directly. Do you know a way to do that ?</p>