title: Why do some built-in Python functions only have pass?
body: <p>I wanted to see how a <code>math.py</code> function was implemented, but when I opened the file in PyCharm I found that all the functions are empty and there is a simple <code>pass</code>. For example:</p>
  
  <pre><code>def ceil(x): # real signature unknown; restored from __doc__
      """
      ceil(x)
  
      Return the ceiling of x as a float.
      This is the smallest integral value &gt;= x.
      """
      pass
  </code></pre>
  
  <p>I guess it is because the functions being used are actually from the C standard library. How does it work? </p>