定义一个类用来表示书籍，有书名，作者，出版社，价格，关键字等属性，获取第一个关键字，获取作者数等方法，再定义一个教辅书类来继承书籍类，新增加教辅科目，年级等属性

class Book:
def __init__(self, title, author, publisher, price, keywords):
self.title = title
self.author = author
self.publisher = publisher
self.price = price
self.keywords = keywords

def get_first_keyword(self):
return self.keywords.split(',')[0]

def get_author_count(self):
return len(self.author.split(','))

class Textbook(Book):
def __init__(self, title, author, publisher, price, keywords, subject, grade):
super().__init__(title, author, publisher, price, keywords)
self.subject = subject
self.grade = grade

book = Book('Python for Beginners', 'John Smith', 'ABC Publishing', 19.99, 'Python,Programming')
print(book.get_first_keyword()) # Python
print(book.get_author_count()) # 1

textbook = Textbook('Mathematics for Elementary School', 'Jane Doe', 'XYZ Publishing', 29.99, 'Math,Education',
'Mathematics', 'Elementary School')
print(textbook.get_first_keyword()) # Math
print(textbook.get_author_count()) # 1