title: Python find elements in one list that are not in the other
body: <p>I need to compare two lists in order to create a new list of specific elements found in one list but not in the other. For example:</p>
  
  <pre><code>main_list=[]
  list_1=["a", "b", "c", "d", "e"]
  list_2=["a", "f", "c", "m"] 
  </code></pre>
  
  <p>I want to loop through list_1 and append to main_list all the elements from list_2 that are not found in list_1.</p>
  
  <p>The result should be:</p>
  
  <pre><code>main_list=["f", "m"]
  </code></pre>
  
  <p>How can I do it with python?</p>