title: Appending values to all keys of python dictionary
body: <p>I have the following dictionary:</p>
  
  <pre><code>dic={'a': {'aa': [], 'ab': [], 'ac': []}, 'b': {'ba': [], 'bb': [], 'bc': []}}
  </code></pre>
  
  <p>I want to append three values to either all keys in 'a' or 'b'.
  Following example works:</p>
  
  <pre><code>dic['a']['aa'].append(value_a)
  dic['a']['ab'].append(value_b)
  dic['a']['ac'].append(value_c)
  </code></pre>
  
  <p>Any way where I can do this in one single line.
  What I'm searching for is something like the following:</p>
  
  <pre><code>dic['a'][*] = [value_a, value_b, value_c]
  </code></pre>
  
  <p>Where * is a wildcard indexing all keys in dic['a'].</p>
  
  <p>As the complexity of the dictionary in my actual program grows my current working example becomes unreadable. So my motivation for this is mainly readability.</p>