title: Display Python >>> prompt in code chunk output
body: <p>We are using rmarkdown to produce a book on Python programming. Code chunk options like <code>eval = TRUE</code> and <code>echo = TRUE</code> can be used to show the nicely formatted code in the output, run it, and show the result within the text.</p>
  
  <p>What would be useful, though, would be to be able to sometimes prepend the code with the Python <code>&gt;&gt;&gt;</code> prompt, to indicate code typed in an interactive terminal.</p>
  
  <p>Is there a way to insert the <code>&gt;&gt;&gt;</code> prompt as a prefix?</p>