title: merge two dictionaries by key
body: <p>I know this question has been asked but I could not find anything that appends the values to the list instead of creating a list of list. I have two dictionaries which have identical values:</p>
  
  <pre><code>dictionary1 = {'1':'one', '2':'two', '3':'three'}
  dictionary2 = {'1':['uno'], '2':['dos'], '3':['tres']}
  </code></pre>
  
  <p>and I need it to return this:</p>
  
  <pre><code>combined = {'1':['one','uno'] '2':['two','dos'] '3':['three',tres']} 
  </code></pre>
  
  <p>so far everything I tried returns this:</p>
  
  <pre><code>combined = {'1':['one'['uno']] '2':['two'['dos']] '3':['three'[tres']]}
  </code></pre>
  
  <p>which has nested lists. How do I append the values of dictionary 1 into the dictionary2 list? Please help me, I know is really simple but I don't know how to do it. thank you </p>
  
  <p>Here is my code:</p>
  
  <pre><code>    combined = {key:[dictionary1[key], dictionary2[key]] for key in dictionary1}
  </code></pre>