Transform list into dictonary with counter values
<p>I have a list, containing project names:</p>

<p><code>my_list = ['a', 'b', 'c', 'a', 'd', 'a', 'a']</code></p>

<p>I want to put the letters into a dictonary, with the key values containing the number, for how many time a letter is in a list:</p>

<pre><code>my_dict = {'a' : 4, 'b' : 1, 'c' : 1, 'd' : 1}
</code></pre>

<p>How can I do this in python?</p>