title: The replace_ending function replaces the old string in a sentence with the new string, but only if the sentence ends with the old string
body: <p>The replace_ending function replaces the old string in a sentence with the new string, but only if the sentence ends with the old string. If there is more than one occurrence of the old string in the sentence, only the one at the end is replaced, not all of them. For example, replace_ending("abcabc", "abc", "xyz") should return abcxyz, not xyzxyz or xyzabc. The string comparison is case-sensitive, so replace_ending("abcabc", "ABC", "xyz") should return abcabc (no changes made).</p>
  
  <pre><code>def replace_ending(sentence, old, new):
  # Check if the old string is at the end of the sentence 
  if ___:
      # Using i as the slicing index, combine the part
      # of the sentence up to the matched string at the 
      # end with the new string
      i = ___
      new_sentence = ___
      return new_sentence
  
  # Return the original sentence if there is no match 
  return sentence
  
  print(replace_ending("It's raining cats and cats", "cats", "dogs")) 
  # Should display "It's raining cats and dogs"
  print(replace_ending("She sells seashells by the seashore", "seashells", 
  "donuts")) 
  # Should display "She sells seashells by the seashore"
  print(replace_ending("The weather is nice in May", "may", "april")) 
  # Should display "The weather is nice in May"
  print(replace_ending("The weather is nice in May", "May", "April")) 
  # Should display "The weather is nice in April"
  </code></pre>