title: Subtracting from len([list]) python
body: <p>I am new in python and wondering for list</p>
  
  <pre><code>a= [blabla, lala, haha, test]
  </code></pre>
  
  <p>can i do a subtraction like</p>
  
  <pre><code>b= 10- len([a])
  </code></pre>
  
  <p>if not whats the way to do subtract from the number of elements in a list? </p>