Python 类方法和静态方法之间的区别

class Book:
    TYPES = ("hardcover", "paperback")  # 精装，平装
    def __init__(self, name, book_type, weight):
        self.name = name
        self.book_type = book_type
        self.weight = weight
    def __repr__(self):
        return f"<Book {self.name}, {self.book_type}, weighing {self.weight}g>"
    def instance_method(self):
        print(f"Called instance method of {self}")
    @classmethod
    def class_method(cls):
        print(f"called class method of {cls}")
    @classmethod
    def hardcover(cls, name, paper_weight):  # cls 名称任意，使用 cls 是 convention
        # 下一行的cls，改成 Book，代码也能跑，但应该写成 cls, 以避免在 inheritance 可能会遇到的问题
        return cls(name, cls.TYPES[0], paper_weight + 100)  # 
    @classmethod
    def paperback(cls, name, paper_weight):
        # 下一行的cls，改成 Book，代码也能跑，但应该写成 cls, 以避免在 inheritance 可能会遇到的问题
        return cls(name, cls.TYPES[1], paper_weight)
    @staticmethod
    def static_method():
        print("Called static method")
book = Book("Dive into Python", Book.TYPES[1], 800)
# Called instance method of <Book Dive into Python, paperback, weighing 800g>
book.instance_method()  
# 下一行代码和上一行完全等价
# Called instance method of <Book Dive into Python, paperback, weighing 800g>
Book.instance_method(book) 
# called class method of <class '__main__.Book'>
Book.class_method()
# Called static method
Book.static_method()
h_book = Book.hardcover("Harry Potter", 1500)
light = Book.paperback("Python 101", 600)
# <Book Harry Potter, hardcover, weighing 1600g>
print(h_book)
# <Book Python 101, paperback, weighing 600g>
print(light)