title: Finding palindromics sequences of length 18 in FASTA file?
body: <p>I want to design guide RNAs to find palindromic sequences in a FASTA file. I want to write a python script that finds all the palindromic sequences of length 18 throughout my sequence. I have a logic in mind but I don't know how to put  it in Python words. My logic is:</p>
  <pre><code>1)If i is [ATCG] and i+17 is [TAGC] then check: 
  2)if i+1 is [ATCG] and i+16 is [TAGC] then check: 
  3)if i+2 is [ATCG] and i+15 is [TAGC] then check&quot;
  .
  .
  .
  
  10)if i+9 is [ATCG] and i+10 is [TAGC] and all the above are true, 
  </code></pre>
  <p>then recognize the sequence of i to i+17 as a palindromic. But I need to make sure that for an A for i it considers only T for i+17.
  Any idea how I write this logic in python?</p>
  <p>Thanks,</p>