title: How to merge two lists, each list contains integer and strings, and I need to do the calculation to get a new list?
body: <p>When I practising Python, I have two lists:</p>
  <pre><code>list_a = [1, 'a', 'c', 'e', 'f'] 
  list_b = [2, 'b', 'c', 'd', 'e'] 
  </code></pre>
  <p>and I want the output is:</p>
  <pre><code>list_c = [3, 'a','b','c','d','e','f']
  </code></pre>
  <p>I tried:</p>
  <pre><code>list_c = [x + y for (x, y) in zip(list_a, list_b)] 
  </code></pre>
  <p>the output is:</p>
  <pre><code>[3, 'ab', 'cc', 'ed', 'fe']
  </code></pre>
  <p>I also tried:</p>
  <pre><code>list_c = set(list_a + list_b)
  </code></pre>
  <p>the output is:</p>
  <pre><code>{1, 2, 'a', 'b', 'c', 'd', 'e', 'f'}
  </code></pre>
  <p>Can someone know how to do it? And the real output is like this:</p>
  <pre><code>list_c = [3, 'a','b','c','d','e','f']
  </code></pre>
  <p>Thanks.</p>