title: I want to recall a python function in vs code but always an error happens. how can I solve it?
body: <pre class="lang-py prettyprint-override"><code>def factorial(n):
      if n&lt;=1:
          return_value=1
          print(return_value)
      else:
          return_value=n*(factorial(n-1))
          print(return_value)
          
  factorial(10)
  </code></pre>
  <p>the error is:</p>
  <blockquote>
  <p>TypeError: unsupported operand type(s) for *: 'int' and 'NoneType'</p>
  </blockquote>