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 xyzxy…

Strings4.py

def replace_ending(sentence, old, new):
	# Check if the old string is at the end of the sentence 
	if sentence.endswith(old):
		# 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 = sentence.rindex(old)
		new_sentence = sentence[:i]+new
		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"