title: Check nested dictionary values?
body: <p>For a large list of nested dictionaries, I want to check if they contain or not a key.
  Each of them may or may not have one of the nested dictionaries, so if I loop this search through all of them raises an error:</p>
  
  <pre><code>for Dict1 in DictionariesList:
       if "Dict4" in Dict1['Dict2']['Dict3']:
           print "Yes"
  </code></pre>
  
  <p>My solution so far is:</p>
  
  <pre><code>for Dict1 in DictionariesList:    
      if "Dict2" in Dict1:
          if "Dict3" in Dict1['Dict2']:
              if "Dict4" in Dict1['Dict2']['Dict3']:
                  print "Yes"
  </code></pre>
  
  <p>But this is a headache, ugly, and probably not very resources effective.
  Which would be the correct way to do this in the first type fashion, but without raising an error when the dictionary doesnt exist?</p>