定义一个图书类，有id，name，price，author，type，press，，在测试类里实现添加到book.txt文件中，实现查询功能，删除功能，修改功能

以下是Python语言实现：

# 定义图书类
class Book:
    def __init__(self, book_id, name, price, author, book_type, press):
        self.book_id = book_id
        self.name = name
        self.price = price
        self.author = author
        self.book_type = book_type
        self.press = press

# 测试类
class BookManager:
    def __init__(self):
        self.books = []
        self.filename = 'book.txt'
        self.load_books()

    # 从文件中加载图书信息
    def load_books(self):
        with open(self.filename, 'r', encoding='utf-8') as f:
            for line in f:
                book_info = line.strip().split(',')
                book = Book(book_info[0], book_info[1], float(book_info[2]), book_info[3], book_info[4], book_info[5])
                self.books.append(book)

    # 将图书信息保存到文件中
    def save_books(self):
        with open(self.filename, 'w', encoding='utf-8') as f:
            for book in self.books:
                f.write(f"{book.book_id},{book.name},{book.price},{book.author},{book.book_type},{book.press}\n")

    # 添加图书
    def add_book(self, book):
        self.books.append(book)
        self.save_books()

    # 删除图书
    def del_book(self, book_id):
        for i, book in enumerate(self.books):
            if book.book_id == book_id:
                self.books.pop(i)
                self.save_books()
                return True
        return False

    # 修改图书信息
    def modify_book(self, book_id, book):
        for i, b in enumerate(self.books):
            if b.book_id == book_id:
                self.books[i] = book
                self.save_books()
                return True
        return False

    # 查询图书信息
    def query_book(self, book_id=None, name=None, author=None, book_type=None, press=None):
        result = []
        for book in self.books:
            if book_id and book.book_id != book_id:
                continue
            if name and book.name != name:
                continue
            if author and book.author != author:
                continue
            if book_type and book.book_type != book_type:
                continue
            if press and book.press != press:
                continue
            result.append(book)
        return result

使用方法：

# 创建图书管理器
book_manager = BookManager()

# 添加图书
book1 = Book('001', 'Python编程从入门到实践', 78.80, 'Eric Matthes', '计算机', '人民邮电出版社')
book_manager.add_book(book1)

# 查询图书
result = book_manager.query_book(name='Python编程从入门到实践')
for book in result:
    print(book.book_id, book.name, book.price, book.author, book.book_type, book.press)

# 修改图书
book2 = Book('001', 'Python编程从入门到入门', 79.90, 'Eric Matthes', '计算机', '人民邮电出版社')
book_manager.modify_book('001', book2)

# 删除图书
book_manager.del_book('001')