title: What does 'r' mean before a Regex pattern?
body: <p>I found the following regex substitution example from the <a href="https://docs.python.org/2/library/re.html" rel="noreferrer">documentation</a> for Regex. I'm a little bit confused as to what the prefix <code>r</code> does before the string?</p>
  
  <pre><code>re.sub(r'def\s+([a-zA-Z_][a-zA-Z_0-9]*)\s*\(\s*\):',
   ...        r'static PyObject*\npy_\1(void)\n{',
   ...        'def myfunc():')
  </code></pre>