s = "In a distant, but not so unrealistic, future where mankind has abandoned earth because it has become covered with trash from products sold by the powerful multi-national Buy N Large corporation, WALLE, a garbage collecting robot has been left to clean up the mess. Mesmerized with trinkets of Earth's history and show tunes, WALLE is alone on Earth except for a sprightly pet cockroach. One day, EVE, a sleek (and dangerous) reconnaissance robot, is sent to Earth to find proof that life is once again sustainable."
print('Количество символов в тексте:\n' + str(len(s)) + '\n')
print('Текст в нижнем регистре:\n' + s.lower() + '\n') # ты написал в нижнем регистре, а в командах предоставленых ниже команда для приведения текста в верхний регистр, если нужно в верхний регистр замени lower на upper
s = s.replace('WALLE', 'WALL-E')
print('Заменено "WALLE" на "WALL-E":\n' + s + '\n')
print('Количество "Earth" в тексте:\n' + str(s.count('Earth')))