Python text search question
<p>I wonder, if you open a text file in Python. And then you'd like to search of words containing a number of letters. </p>

<p>Say you type in 6 different letters (a,b,c,d,e,f) you want to search.
You'd like to find words matching at least 3 letters.
Each letter can only appear once in a word.
And the letter 'a' always has to be containing. </p>

<p>How should the code look like for this specific kind of search?</p>
