title: Python counting DNA nucleotides
body: <blockquote>
    <p><strong>Problem</strong></p>
    
    <p>A string is simply an ordered collection of symbols selected from some
    alphabet and formed into a word; the length of a string is the number
    of symbols that it contains.</p>
    
    <p>An example of a length 21 DNA string (whose alphabet contains the
    symbols <code>'A'</code>, <code>'C'</code>, <code>'G'</code>, and <code>'T'</code>) is <code>"ATGCTTCAGAAAGGTCTTACG."</code></p>
    
    <p><strong>Given:</strong> A DNA string s</p>
    
    <p>of length at most 1000 nt.</p>
    
    <p><strong>Return:</strong> Four integers (separated by spaces) counting the respective number of times that the symbols 'A', 'C', 'G', and 'T'
    occur in s</p>
    
    <p><strong>Sample Dataset</strong></p>
  
  <pre><code>AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC
  </code></pre>
    
    <p><strong>Sample Output</strong></p>
  
  <pre><code>20 12 17 21
  </code></pre>
  </blockquote>
  
  <p>can someone help me figure this code for python 3 on a mac? I am sorry I am totally not accustomed with python</p>