title: Python3 print string formatting
body: <p>Is it recommend to format a string :</p>
  
  <pre><code>var = 'python 3'
  print(f"This is {var}") # prints out This is python 3
  </code></pre>
  
  <p>or</p>
  
  <pre><code>var = 'python 3'
  print("This is", var)
  </code></pre>
  
  <p>or the old string formatting</p>
  
  <pre><code>var = 'python 3'
  print("This is %s" % var)
  </code></pre>
  
  <p>Also, is <code>print(f"{var}")</code> a new feature to python 3.6? I got <code>SyntaxError: invalid syntax</code> when running the same code in python 3.5.3.</p>