Python 20 json、pickle、shelve序列化模块

dic = {‘k1‘:‘v1‘}
json  dumps序列化方法  loads反序列化方法  : 对内存操作
print(type(dic),dic)
import json
str_d = json.dumps(dic)
print(type(str_d),str_d)

dic_d = json.loads(str_d)
print(type(dic_d),dic_d)

import json
dic = {‘a‘:1,‘b‘:2}
f = open(‘fff‘,‘w‘,encoding=‘utf-8‘)
json.dump(dic,f)
f.close()

f = open(‘fff‘)
res = json.load(f)
f.close()
print(res,type(res))

import json
dic = {‘a‘:‘中国‘,‘b‘:‘国家‘}
f = open(‘fff‘,‘w‘,encoding=‘utf-8‘)
json.dump(dic,f,ensure_ascii=False)  # 这里加一个 ensure_ascii=False
f.close()

f = open(‘fff‘,encoding=‘utf-8‘)
res = json.load(f,)
f.close()
print(res,type(res))

import json
l = [{‘k‘:111},{‘k‘:111},{‘k‘:111}]
f = open(‘file‘,‘w‘)
for dic in l:
    str_dic = json.dumps(dic)
    f.write(str_dic+‘\n‘)
f.close()

l = []
f = open(‘file‘)
for line in f:
   dic = json.loads(line.strip())
   l.append(dic)
f.close()
print(l)

import pickle
dic = {‘k1‘:‘v1‘,‘k2‘:‘v2‘,‘k3‘:‘v3‘}
str_dic = pickle.dumps(dic)
print(str_dic)  # 一串二进制内容

dic2 = pickle.loads(str_dic)
print(dic2)  #  字典

import time
struct_time = time.localtime(1000000000)
print(struct_time)
f = open(‘pick_file‘,‘wb‘)
pickle.dump(struct_time,f)
f.close()

f = open(‘pick_file‘,‘rb‘)
struct_time2 = pickle.load(f)
print(struct_time2.tm_year)
f.close()

import time
struct_time1 = time.localtime(1000000000)
struct_time2 = time.localtime(2000000000)
# print(struct_time)
f = open(‘pick_file‘,‘wb‘)
pickle.dump(struct_time1,f)
pickle.dump(struct_time2,f)
f.close()

f = open(‘pick_file‘,‘rb‘)
struct_time3 = pickle.load(f)
struct_time4 = pickle.load(f)
print(struct_time3.tm_year)
print(struct_time4.tm_year)
f.close()

import shelve
f = shelve.open(‘shelve_file‘)
f[‘key‘] = {‘int‘:10,‘float‘:9.5,‘string‘:‘sample data‘} # 直接对文件句柄操作,就可以修改数据
f.close()

import shelve
f1 = shelve.open(‘shelve_file‘)
existing = f1[‘key‘]  # 取出数据时,只需要直接用key获取即可,但是如果key不存在,会报错
f1.close()
print(existing)

第一种
import shelve
f = shelve.open(‘shelve_file‘,flag=‘c‘)
existing = f[‘key‘]
f.close()
print(existing)

第二种
import shelve
f = shelve.open(‘shelve_file‘,flag=‘r‘)
existing = f[‘key‘]
f[‘key‘] = 10  # 这样就把key的值全改了
f.close()
print(existing)

f = shelve.open(‘shelve_file‘,flag=‘r‘)
existing2 = f[‘key‘]
f.close()
print(existing2)

import shelve
f1 = shelve.open(‘shelve_file‘)
print(f1[‘key‘])
f1[‘key‘][‘new value‘] = ‘this was not here before‘
f1.close()

import shelve
f1 = shelve.open(‘shelve_file‘,writeback=True)
print(f1[‘key‘])
f1[‘key‘][‘new value‘] = ‘this was not here before‘
f1.close()