title: python regular expression specific characters, any combination
body: <p>So I'm trying to create a regex clause where it can detect any combination of <strong>'ACTG'</strong> characters, and accept that as valid. While anything else - including a combination of <strong>'ACTG'</strong> and some other characters are invalid.</p>
  
  <p>Ultimately, I'll take it out of the while loop, that's just for testing purposes.  Right now I believe as long as it starts with either a, c, t, or g, it says it's valid.... </p>
  
  <p>Is there a funcition in regex that would be better suited than match?</p>
  
  <pre><code>import re
  while (True):
      DnaString = str(input('enter your polynucleotide chain code hooblah'))
      if (re.match('([ACTG]+[ACTG]*)', DnaString, flags=0)):
          #if re.search('^ACTG', DnaString) != -1: 
              print ("valid chain.")
      else: #(re.search('^[ACTG]+[ACTG]*$', DnaString) == -1):
          print("invalid chain, please check your input.")
  
      if (DnaString.find("end") != -1):
          print("ohokaybye.")
          break
  </code></pre>