title: Python how to match files to templates
body: <p>I'm looking to match many files against some common templates, and extract the differences. I'd like suggestions on the best way to do this. For example:</p>
  
  <p>Template A:</p>
  
  <pre><code>&lt;1000 text lines that have to match&gt;
  a=?
  b=2
  c=3
  d=?
  e=5
  f=6
  &lt;more text&gt;
  </code></pre>
  
  <p>Template B:</p>
  
  <pre><code>&lt;1000 different text lines that have to match&gt;
  h=20
  i=21
  j=?
  &lt;more text&gt;
  k=22
  l=?
  m=24
  &lt;more text&gt;
  </code></pre>
  
  <p>If I passed in file C:</p>
  
  <pre><code>&lt;1000 text lines that match A&gt;
  a=500
  b=2
  c=3
  d=600
  e=5
  f=6
  &lt;more text&gt;
  </code></pre>
  
  <p>I'd like an easy way to say this matches template A, and extract 'a=500', 'd=600'.</p>
  
  <p>I could match these with a regex, but the files are rather large, and building that regex would be a pain.</p>
  
  <p>I've also tried difflib, but parsing the opcodes and extracting the differences doesn't seem optimal.</p>
  
  <p>Anyone have a better suggestion?</p>