title: How to check a key is in dictionary which store in list
body: <p>demo code</p>
  <pre><code>lst = [{'foo':1}, {'bar':2}]
  </code></pre>
  <p>===================</p>
  <pre><code>'foo' in lst 
  </code></pre>
  <p>return False as the key is inside the dictionary which need to explicitly use</p>
  <pre><code>'foo' in lst[0]
  </code></pre>
  <p>Is there a way to return boolean but without giving the magic number?
  for loop is not under consideration if the list is many and it gives troubles to append for not exist key as dictionary.</p>