title: Python add missing element into list
body: <p>I have a list with day of a month as key and i want to add all missing day with 0 as value.</p>
  <p>This is a sample :</p>
  <pre><code>tab = [{'day':3, 'value':50, 'label': 'Element 1' }, {'day':5, 'value':20, 'label': 'Element 2'},{'day':11, 'value':3, 'label': 'other label'},{'day':15, 'value':5, 'label': 'something'}]
  </code></pre>
  <p>And I looking for something like this :</p>
  <pre><code>tab = [{'day':1, 'value':0, 'label': 'some label'}, {'day':2, 'value':0, ‘label': 'something'}, ...,{'day':30, 'value':0, 'label': 'value label'}]
  </code></pre>
  <p>What is the better way to did it.</p>
  <p>This is my code :</p>
  <pre><code>new_tab = []
  for i in range(1, 30):
      if i not in existing_day:
          new_tab.append({'day': i, 'value': 0, 'label':''})
      else:
          elt = [x for x in tab if x['day'] == i]
          new_tab.append(elt[0])
  </code></pre>