import json
class Book():
    def __init__(self,id,category,year,author):
        self.id=id
        self.category=category
        self.year=year
        self.author=author

    def print_sth(self):
        print( "书的编号是%s类别是%s年代%s作者是%s"%(self.id,self.category,self.year,self.author))

    def obj_detail(self,obj):
        return {
                    "id":obj.id,
                    "category":obj.category,
                    "year":obj.year,
                    "author":obj.author
                      }
Book1=Book(1,2019,"prose","Tom")
js=json.dumps(Book1,default=Book1.obj_detail)
print(type(js))
print(js)
Book1.print_sth()

方法二
import json
class Book():

    def __init__(self,id,category,year,author):
        self.id=id
        self.category=category
        self.year=year
        self.author=author

Book1=Book(1,2019,"prose","Tom")
js=json.dumps(Book1,default=lambda Book1:Book1.__dict__)
print(js)
print(type(js))

将实例东西编码成为json串的2种方法