title: How to remove numerical x-ticks under custom labels in matplotlib's boxplot?
body: <p>I want to plot multiple boxplots (using matplotlib in python3) into one figure and label them accordingly along the x axis. I have tried multiple methods to set custom x-ticks, but the old, numerical ticks always show through.</p>
  
  <p>The following two code snippets yield the same result. In the first one, I use <code>plt.xticks(ticks, labels, rotation='vertical')</code> to set the ticks (also does not work w.o. rotation). 
  In both cases <code>compressed_runs</code> is a dict, where the keys coincide with the x-ticks' labels and the values are numeric arrays.</p>
  
  <pre class="lang-py prettyprint-override"><code>plt.figure(figsize=[10, 8], dpi=300)
  labels = ['test']*len(compressed_runs)
  ticks = [i+1 for i, v in enumerate(compressed_runs)]
  
  plt.xticks(ticks, labels, rotation='vertical')
  plt.ylabel('communication times [µs]')
  plt.title('Test title')
  
  plt.boxplot(compressed_runs.values(), showfliers=False)
  plt.savefig(plotname)
  plt.close()
  </code></pre>
  
  <p>I also tried modifying the figure's axes directly:</p>
  
  <pre class="lang-py prettyprint-override"><code>fig = plt.figure(figsize=[10, 8], dpi=300)
  labels = ['test']*len(compressed_runs)
  ticks = [i+1 for i, v in enumerate(compressed_runs)]
  
  plt.xticks(ticks, labels, rotation='vertical')
  fig.axes[0].set_xticklabels(labels)
  plt.ylabel('communication times [µs]')
  plt.title('Test title')
  
  plt.boxplot(compressed_runs.values(), showfliers=False)
  plt.savefig(plotname)
  plt.close()
  </code></pre>
  
  <p><img src="https://i.ibb.co/3d8Wm8J/33nodes-1-B-txt-json-boxplot.png" alt="obscured x-ticks"></p>
  
  <p>As you can see in the figure, the enumerated x-ticks still show through from underneath the named x-ticks. In this case I expect only 'test' to be under each boxplot.</p>