python day28--json,pickle,hashlib,logging

一、json格式的限制

1.json格式的key必须是字符串数据类型，如果是数字dumps后会被转为字符串。

# dic = {1:2,3:4}
# str_dic = json.dumps(dic)
# print(str_dic)
# new_dic = json.loads(str_dic)
# print(new_dic)

2.元组可以作为vaule但会被转为列表，并且不能作为key

3.可以多次将数据dump进文件，但不能load出来。

# dic = {'abc':(1,2,3)}
# lst = ['aaa',123,'bbb',12.456]
# with open('json_demo','w') as f:
#     json.dump(lst,f)
#     json.dump(dic,f)
# with open('json_demo') as f:
#     ret = json.load(f)
#     print(ret)
#报错

 4.想多次dump并load出来

dic = {'abc':(1,2,3)}
lst = ['aaa',123,'bbb',12.456]
with open('json_demo','w') as f:
    str_lst = json.dumps(lst)
    str_dic = json.dumps(dic)
    f.write(str_lst+'
')
    f.write(str_dic+'
')

with open('json_demo') as f:
    for line in f:
        ret = json.loads(line)
        print(ret)

二、pickl

1.dump的结果是bytes,dump用的f文件句柄需要以wb的形式打开,load所用的f是'rb'模式

2.pickle支持几乎所有对象的

把对象写入，及读出

# class Student:
#     def __init__(self,name,age):
#         self.name = name
#         self.age = age
#
# alex = Student('alex',83)
# ret = pickle.dumps(alex)
# 小花 = pickle.loads(ret)
# print(小花.name)
# print(小花.age)

# class Student:
#     def __init__(self,name,age):
#         self.name = name
#         self.age = age
#
# alex = Student('alex',83)
# with open('pickle_demo','wb') as f:
#     pickle.dump(alex,f)
# with open('pickle_demo','rb') as f:
#     旺财 = pickle.load(f)
#     print(旺财.name)

三、hashlib

1.

# 能够把 一个 字符串 数据类型的变量
# 转换成一个 定长的 密文的 字符串,字符串里的每一个字符都是一个十六进制数字
背下来

# md5_obj = hashlib.md5()#或者sha1等
# md5_obj.update(s1.encode('utf-8'))#encode必须要
# res = md5_obj.hexdigest()
# print(res,len(res),type(res))

2.动态加盐，更加安全

# username = input('username : ')
# passwd = input('password : ')
# md5obj = hashlib.md5(username.encode('utf-8'))
# md5obj.update(passwd.encode('utf-8'))
# print(md5obj.hexdigest())

3.文件一致性检验

# md5_obj = hashlib.md5()
# with open('5.序列化模块_shelve.py','rb') as f:
#     md5_obj.update(f.read())
#     ret1 = md5_obj.hexdigest()
#
# md5_obj = hashlib.md5()
# with open('5.序列化模块_shelve.py.bak','rb') as f:
#     md5_obj.update(f.read())
#     ret2 = md5_obj.hexdigest()
# print(ret1,ret2)