Day⑥:shelve Module

Shelve module

The shelve module is a simple k,v module that persists memory data through a file and can persist any Python data format that pickle can support

Frankly, it's Pickle's senior.

Example:

I. Pickle processing data formats for Python

①pickle_dump.py

  
 

   
  

  
#!/usr/bin/env python
   
  

  
#coding=utf-8
   
  

  

   
  

  
#这个例子是pickle dump对比shelve之持久化
   
  

  

   
  

  

   
  

  
import pickle
   
  

  

   
  

  
class Test(object):
   
  

  
 def __init__(self,n):
   
  

  
 self.n=n
   
  

  

   
  

  

   
  

  
t=Test(123)
   
  

  
t2=Test(456)
   
  

  

   
  

  
name=["yaobin","test","haha"]
   
  

  

   
  

  

   
  

  

   
  

  
f=open("pickle_test.pk1",‘wb‘)
   
  

  
pickle.dump(t,f) #把t类dump进去
   
  

  
pickle.dump(t2,f) #把t2类dump进去
   
  

  
pickle.dump(name,f) #把列表也dump进去
   
  

  
f.close()
  
 

②pickle_load.py

  
 

   
  

  
#!/usr/bin/env python
   
  

  
#coding=utf-8
   
  

  

   
  

  
#这个例子主要pickle load对比shelve之取值
   
  

  

   
  

  
import pickle
   
  

  

   
  

  
f=open("pickle_test.pk1","rb")
   
  

  

   
  

  
#pickle的load 是先dump进去的，先出来，先进先出
   
  

  

   
  

  
#第一次load
   
  

  
a=pickle.load(f)
   
  

  
print(a.n)
   
  

  

   
  

  
#第二次load
   
  

  
b=pickle.load(f)
   
  

  
print(b.n)
   
  

  

   
  

  
#第三次load
   
  

  
c=pickle.load(f)
   
  

  
print(c)
   
  

  

   
  

  
#总结: 不能随时的load我想要的东西出来啊，所以才有shelve，可以使用key的方式持久化，再通过key取出来。
   
  

  

   
  

  

   
  

  

   
  

  
#结果
   
  

  
123
   
  

  
456
   
  

  
[‘yaobin‘, ‘test‘, ‘haha‘]
  
 

two. Shelve processing python's data format①shelve the persistence of the. py

  
 

   
  

  
#!/usr/bin/env python
   
  

  
#coding=utf-8
   
  

  

   
  

  

   
  

  
import shelve
   
  

  

   
  

  
d = shelve.open(‘shelve_test‘) #打开一个文件
   
  

  

   
  

  
class Test(object):
   
  

  
 def __init__(self,n):
   
  

  
 self.n = n
   
  

  

   
  

  

   
  

  
t1 = Test(123) #实例化
   
  

  
t2 = Test(456) #实例化
   
  

  

   
  

  
name = ["alex","rain","test"] #列表
   
  

  

   
  

  

   
  

  
d["list"] = name #持久化列表
   
  

  
d["t1"] = t1 #持久化类
   
  

  
d["t2"] = t2 #持久化类
   
  

  

   
  

  
d.close()
  
 

Value of ②shelve. py

  
 

   
  

  
#!/usr/bin/env python
   
  

  
#coding=utf-8
   
  

  

   
  

  

   
  

  
import shelve
   
  

  

   
  

  
a=shelve.open(‘shelve_test‘) #打开一个文件
   
  

  

   
  

  

   
  

  
#用shelve的get方法取出key对应的值，比pickle load 要好
   
  

  
h1=a.get("list")
   
  

  
h2=a.get("t1")
   
  

  
h3=a.get("t2")
   
  

  

   
  

  
print(h1)
   
  

  
print(h2.n)
   
  

  
print(h3.n)
   
  

  

   
  

  

   
  

  
#结果
   
  

  
[‘alex‘, ‘rain‘, ‘test‘]
   
  

  
123
   
  

  
456
  
 

From for notes (Wiz)

Day⑥:shelve Module