pickle不便于把多个对象存储在一个文件里

shelve //更适用于自定义的类

import shelve

scores = [99,88,77]

student = {'name':'Mike', 'age':20}

db = shelve.open('shelve_student') //创建为二进制

db['s'] = student

db['scores'] = scores

len(db)  //2

temp_student = db['s']

type(temp_student)

del db['scores'] 

class Student:

    def __init__(self,name,age):

        self.name = name

        self.age = age

    def__str__(self):

        return self.name

def write_shelve():

    s =Student('Tom', 20)

    db = shelve.open('shelve_student_db')

    db['s'] = s

    db.close()

def read_shelve():

    db = shelve.open('shelve_student_db')

    st = db['s']

    db.close()

if __name__ =='__main__':

    read_shelve()

    read_shelve()