title: checkin python if a list of dictonaries does NOT contain a specific value
body: <p>This is some what of a supplementary question to my recent query about searching dictionary items in a list:</p>
  
  <p><a href="https://stackoverflow.com/questions/8695177/check-if-python-dictionary-contains-value-and-if-so-return-related-value">Check if python dictionary contains value and if so return related value</a></p>
  
  <p>I have an array containing dictionaries in the format:</p>
  
  <pre><code>fileList = [
                 {"fileName": "file1.txt", "fileMod": "0000048723"}, 
                 {"fileName": "file2.txt", "fileMod": "0000098573"}
             ]
  </code></pre>
  
  <p>I was able to return a list of fileMod values for existing items in the fileList using 
  a rather neat list comprehension as suggested:</p>
  
  <pre><code>fileMod = [item['fileMod'] for item in fileList if item['fileName'] == filename]
  </code></pre>
  
  <p>This returns a value if there is a matching filename, but I forgot to include that I also need to know when there is a filename that does not match any of the entries in filelist. </p>
  
  <p>I am sure this should be simple, but I think I have just been looking at it too long to see the woods for the trees.</p>