title: What is the default GUI backend for Matplotlib?
body: <p>I have made the following script, let's call it <code>test-matplotlib-printbackend.py</code>:</p>
  
  <pre class="lang-python prettyprint-override"><code>#!/usr/bin/env python
  
  import matplotlib as mpl
  import matplotlib.pyplot as plt
  
  xx = range(100)
  yy = [i*2+5 for i in xx]
  
  fig, ax = plt.subplots()
  ax.plot(xx, yy)
  
  print("Matplotlib plt backend: {}".format(plt.get_backend()))
  
  plt.show()
  </code></pre>
  
  <p>For Python3 under MINGW64 on Windows 10, as well as Python3 under Anaconda on Windows 10, I get the printout:</p>
  
  <pre><code>Matplotlib plt backend: Qt5Agg
  </code></pre>
  
  <p>However, for Python3 on Rasbian (Raspberry Pi's Debian OS), I get the printout:</p>
  
  <pre><code>Matplotlib plt backend: TkAgg
  </code></pre>
  
  <p>This kind of puzzles me, because I sort of expected TkAgg would be the default GUI backend for matplotlib on <em>all</em> platforms !?</p>
  
  <p>So, I just wanted to know - is the default GUI backend for Matplotlib for different platforms documented anywhere?</p>