title: Determine line number in Python 3.9
body: <p>Since<code>sys._getframe().f_back.f_lineno</code> does not work at all in <strong>python 3.9</strong>, following could be used from now:</p>
  <pre><code>from inspect import currentframe
  
  
  def testLineNumberFunction() -&gt; int:
      return currentframe().f_back.f_lineno
  
  
  print(f'line number is {testLineNumberFunction()}')
  </code></pre>
  <p>Result:</p>
  <pre><code>line number is 8
  </code></pre>
  <p><strong>Is there a faster way to achieve this ?</strong></p>
  <p>Because the library <strong>inspect</strong> seems to be <strong>slow</strong> as mentioned here <a href="https://stackoverflow.com/a/17366561/5667103">by @AlexGranovsky</a></p>