Let's count sentences in the text. Perform sentence tokenization (using nltk) on the given text and select the number of sentences after the tokenization:
text = '''Louis XVI (born 1754 A.D.) also encouraged major voyages of exploration.
In 1785, he appointed La Pérouse to lead a sailing expedition around the world.
(La Pérouse and his fleet disappeared after leaving Botany Bay in March 1788.
Louis is recorded as having asked, on the morning of his execution, "Any news of La Pérouse?".)'''Please, take into account the following — this tokenizer checks dots inside brackets, too. It also doesn't recognize typical abbreviations as the sentence end and a dot before a bracket.