title: Python match a string with regex
body: <p>I need a python regular expression to check if a word is present in a string. The string is separated by commas, potentially.</p>
  
  <p>So for example,</p>
  
  <pre><code>line = 'This,is,a,sample,string'
  </code></pre>
  
  <p>I want to search based on "sample", this would return true. I am crappy with reg ex, so when I looked at the python docs, I saw something like</p>
  
  <pre><code>import re
  re.match(r'sample', line)
  </code></pre>
  
  <p>But I don't know why there was an 'r' before the text to be matched. Can someone help me with the regular expression?</p>