title: how to seperate numbers from a string optimally
body: <p>I'd like to remove strings in my list.
  <br>Suppose,
  <br> <strong>x = ['feature 1' , 'feature 2' , 'feature 3' , 'feature 4']</strong>
  <br><br>
  I want to achieve, <br>
  <strong>x = [1, 2, 3, 4]</strong>
  <br><br>
  I know this can be achieved by splitting each individual element and removing the <strong>feature</strong> term and retaining the remaining value. <br><br> <strong>BUT</strong> <BR><br>
  i want to create a common function to achieve something like this and more optimal function rather than extracting each indiviual element and doing it.. It's cumbersome. <br> <br><strong>INSTEAD</strong><br><br>
  I want a solution which auto detects the strings and removes it in each element. <br> <br> <strong>NOW THAT'S OPTIMAL</strong> <br> Please let me know below if there's anything like it.</p>