python的对象数据库ZODB的使用（python3经典编程案例）

一. 概述

ZODB是一个可拓展和冗余的数据库，专注于存储可拓展的对象。

使用ZODB的好处：

• 使对象持久化对代码几乎没有影响，代码和数据库之间几乎没有接缝。
• 没有部分隐藏数据库的数据库映射程序。
• 象之间的关系处理得非常自然，支持没有连接的复杂对象图。
• 数据本地保存，不需要安装软件和搭建环境。

官方文档：http://www.zodb.org/en/latest/

安装：pip install ZODB

二. 基本使用

1. 存储数据

# -*-coding: UTF-8 -*-
from ZODB import FileStorage, DB
import transaction


class MyZODB(object):
    def __init__(self, path):
        self.storage = FileStorage.FileStorage(path)
        self.db = DB(self.storage)
        self.connection = self.db.open()
        self.dbroot = self.connection.root()

    def close(self):
        self.connection.close()
        self.db.close()
        self.storage.close()


db = MyZODB('./Data.fs')
dbroot = db.dbroot
dbroot['a_number'] = 3
dbroot['a_string'] = 'Gift'
dbroot['a_list'] = [1, 2, 3, 5, 7, 12]
dbroot['a_dictionary'] = {
    1918: 'Red Sox', 1919: 'Reds' }
dbroot['deeply_nested'] = {
   
 1918: [('Red Sox', 4), ('Cubs', 2)],
 1919: [('Reds', 5), ('White Sox', 3)],
}
transaction.commit()
db.close()

2. 获取数据

# -*-coding: UTF-8 -*-
from ZODB import FileStorage, DB
import transaction


class MyZODB(object):
    def __init__(self, path):
        self.storage = FileStorage.FileStorage(path)
        self.db = DB(self.storage)
        self.connection = self.db.open()
        self.dbroot = self.connection.root()

    def close(self):
        self.connection.close()
        self.db.close()
        self.storage.close()


db = MyZODB('./Data.fs')
dbroot = db.dbroot
for key in dbroot.keys():
    print(key + ':', dbroot[key])
db.close()

3. 更改数据

# -*-coding: UTF-8 -*-
from ZODB import FileStorage, DB
import transaction


class MyZODB(object):
    def __init__(self, path):
        self.storage = FileStorage.FileStorage(path)
        self.db = DB(self.storage)
        self.connection = self.db.open()
        self.dbroot = self.connection.root()

    def close(self):
        self.connection.close()
        self.db.close()
        self.storage.close()


db = MyZODB('./Data.fs')
dbroot = db.dbroot
# dbroot['a_string'] = 'Gift啊'
# transaction.commit()
# db.close()

# 更改字典数据时
a_dict = dbroot['a_dictionary']
a_dict[1920] = '1234567'
# 设置数据库的根属性，通知他需要重新存储其下的属性
dbroot._p_changed = 1
transaction.commit()
db.close()

4. 删除数据

# -*-coding: UTF-8 -*-
from ZODB import FileStorage, DB
import transaction


class MyZODB(object):
    def __init__(self, path):
        self.storage = FileStorage.FileStorage(path)
        self.db = DB(self.storage)
        self.connection = self.db.open()
        self.dbroot = self.connection.root()

    def close(self):
        self.connection.close()
        self.db.close()
        self.storage.close()


db = MyZODB('./Data.fs')
dbroot = db.dbroot
del dbroot['a_number']
transaction.commit()
db.close()

三. 综合案例：模拟银行存取款系统

# -*-coding: UTF-8 -*-
import ZODB
import ZODB.FileStorage as ZFS
import transaction


import persistent


class OutOfFunds(Exception):
    pass


class Account(persistent.Persistent):
    def __init__(self, name, start_balance=0):
        self.name = name
        self.balance = start_balance

    def __str__(self):
        return f"Account: {self.name}, balance: {self.balance}"

    def __repr__(self):
        return f"Account: {self.name}, balance: {self.balance}"

    def deposit(self, amount):
        """save amount into balance"""
        self.balance += amount

    def withdraw(self, amount):
        """withdraw from balance"""
        if amount > self.balance:
            raise OutOfFunds
        self.balance -= amount
        return self.balance


class ZODBUtils:
    conn = None
    filestorage = None

    def openConnection(self,file_name):
        self.filestorage = ZFS.FileStorage(file_name)
        db = ZODB.DB(self.filestorage)
        self.conn = db.open()
        return self.conn

    def closeConnection(self):
        self.conn.close()
        self.filestorage.close()


def init_balance():
    zodbutils = ZODBUtils()
    conn = zodbutils.openConnection('zodb_filestorage.db')
    root = conn.root()

    noah = Account('noah', 1000)
    print(noah)
    root['noah'] = noah

    jermy = Account('jermy', 2000)
    print(jermy)
    root['jermy'] = jermy

    transaction.commit()
    zodbutils.closeConnection()


def app():
    zodbutils = ZODBUtils()
    conn = zodbutils.openConnection('zodb_filestorage.db')
    root = conn.root()
    noah = root['noah']
    print("Before Deposit Or Withdraw")
    print("=" * 30)
    print(noah)
    jermy = root['jermy']
    print(jermy)
    print('-' * 30)

    transaction.begin()
    noah.deposit(300)
    jermy.withdraw(300)
    transaction.commit()

    print("After Deposit Or Withdraw")
    print("=" * 30)
    print(noah)
    print(jermy)
    print("-" * 30)
    zodbutils.closeConnection()


if __name__ == '__main__':
    init_balance()
    app()