Append to the python's dictionary key:value
<p>I have a question about the dictionary in python, in the reference page: <a href="http://docs.python.org/tutorial/datastructures.html#dictionaries" rel="nofollow">http://docs.python.org/tutorial/datastructures.html#dictionaries</a> . </p>

<blockquote>
  <p>"You can’t use lists as keys, since lists can be modified in
  place using index assignments, slice assignments, or methods like
  append() and extend()."</p>
</blockquote>

<p>But what does it mean to append the value of a python dictionary?</p>

<pre><code># A simple program that keep track of the line number(s) a word appeared in the novel
myDictionary = {} 
    with open('novel.txt') as book:
        lineNumber = 1
        for line in book:
            # cleaned is a helper function to clean up the line
            for word in cleaned(line).split():
                if word in myDictinoary:
                    myDictionary[word].append(lineNumber)
                else:
                    myDiciontary[word]=[lineNumber]
            lineNumber += 1
</code></pre>

<p>What exactly is going on when <code>myDictionary[word].append(lineNumber)</code> ? It seems to me a list, I want to be sure, the value of a key can be list (or in this case it is an Tuples)? <strong>What kind of data type exactly can be used as a value? When I want the key to store multiple values.</strong></p>
