Home Backend Development Python Tutorial Python中的anydbm模版和shelve模版使用指南

Python中的anydbm模版和shelve模版使用指南

Jun 10, 2016 pm 03:09 PM
python

好久没写这系列的文章了,我越来越喜欢用python了,它在我的工作中占据的比例越来越大。废话少说,直接进入主题。

 anydbm允许我们将一个磁盘上的文件与一个“dict-like”对象关联起来,操作这个“dict-like”对象,就像操作dict对象一样,最后可以将“dict-like”的数据持久化到文件。对这个”dict-like”对象进行操作的时候,key和value的类型必须是字符串。下面是使用anydbm的例子:
   

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#coding=utf-8

  

import anydbm

  

def CreateData():

  try:

    db = anydbm.open('db.dat', 'c')

     

# key与value必须是字符串

     

# db['int'] = 1

     

# db['float'] = 2.3

    db['string'] = "I like python."

    db['key'] = 'value'

  finally:

    db.close()

  

def LoadData():

  db = anydbm.open('db.dat', 'r')

  for item in db.items():

    print item

  db.close()

  

if __name__ == '__main__':

  CreateData()

  LoadData()

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anydbm.open(filename[, flag[, mode]]),filename是关联的文件路径,可选参数flag可以是: ‘r': 只读, ‘w': 可读写, ‘c': 如果数据文件不存在,就创建,允许读写; ‘n': 每次调用open()都重新创建一个空的文件。mode是unix下文件模式,如0666表示允许所有用户读写。
shelve模块是anydbm的增强版,它支持在”dict-like”对象中存储任何可以被pickle序列化的对象,但key也必须是字符串。同样的例子,与shelve来实现:

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import shelve

  

def CreateData():

  try:

    db = shelve.open('db.dat', 'c')

     

# key与value必须是字符串

    db['int'] = 1

    db['float'] = 2.3

    db['string'] = "I like python."

    db['key'] = 'value'

  finally:

    db.close()

  

def LoadData():

  db = shelve.open('db.dat', 'r')

  for item in db.items():

    print item

  db.close()

  

if __name__ == '__main__':

  CreateData()

  LoadData()

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