帮我生成一个图书管理借书，还书的python代码

好的，以下是一个简单的图书管理系统的Python代码：

class Book:
    def __init__(self, title, author, isbn):
        self.title = title
        self.author = author
        self.isbn = isbn
        self.available = True
    
    def __str__(self):
        return f"{self.title} by {self.author}"
    
    def check_out(self):
        self.available = False
        
    def check_in(self):
        self.available = True

class Library:
    def __init__(self):
        self.books = []
    
    def add_book(self, book):
        self.books.append(book)
    
    def remove_book(self, book):
        self.books.remove(book)
    
    def search_book(self, search_term):
        results = []
        for book in self.books:
            if search_term.lower() in book.title.lower() or search_term.lower() in book.author.lower():
                results.append(book)
        return results
    
    def check_out_book(self, book):
        if book.available:
            book.check_out()
            print(f"{book} has been checked out.")
        else:
            print(f"{book} is not available.")
    
    def check_in_book(self, book):
        if not book.available:
            book.check_in()
            print(f"{book} has been checked in.")
        else:
            print(f"{book} has already been checked in.")

这个系统包括两个类：Book和Library。Book类表示一本书，它有一个标题，作者和ISBN号。它还有一个可用属性，表示这本书是否可用。Library类表示整个图书馆，它有一个书本列表，可以添加，删除和搜索书籍。它还有一个check_out_book方法和check_in_book方法，用于借书和还书。

你可以通过以下方式使用这个系统：

book1 = Book("The Great Gatsby", "F. Scott Fitzgerald", "978-0743273565")
book2 = Book("To Kill a Mockingbird", "Harper Lee", "978-0446310789")
book3 = Book("1984", "George Orwell", "978-0451524935")

library = Library()
library.add_book(book1)
library.add_book(book2)
library.add_book(book3)

results = library.search_book("Orwell")
print("Search results:")
for book in results:
    print(book)

library.check_out_book(book3)
library.check_out_book(book3)
library.check_in_book(book3)
library.check_in_book(book3)

这将输出以下内容：

Search results:
1984 by George Orwell
1984 has been checked out.
1984 is not available.
1984 has been checked in.
1984 has already been checked in.