title: Remove exact alphanumeric string from text in R/Python
body: <p>"The string? is made up a load of strings but the problem is the removal of question mark in the word string? without removing the other question marks. can anybody have a look?"   </p>
  
  <p>In the above text I have to alter "string?" to "string". But I dont want the statement to lose the rest of the ? in the text.</p>
  
  <p>Resultant text should be:
  "The string is made up a load of strings but the problem is the removal of question mark in the word string without removing the other question marks. can anybody have a look?"   </p>
  
  <p>I have tried gsub, string_replace and a number of other methods, they end up removing or replacing the word and still keeping the "?"</p>