title: string variable as latex in pyplot
body: <p>It is possible to have Latex formatting in pyplot diagrams, i.e. for title, labels etc. </p>
  
  <pre><code>#some dummy code
  plt.plot(x,y,label = r"$a &lt; \gamma$")
  </code></pre>
  
  <p>It is generated by adding an r before the actual latex string.
  Now, pyplot accepts variables as inputs for strings, i.e.</p>
  
  <pre><code>#some dummy code
  foo = "some fancy label"
  plt.plot(x,y, label = foo)
  </code></pre>
  
  <p>I would like to combine the two worlds, however the only answer I found on SO is for Julia.</p>
  
  <p>How can I make this work?</p>