python的对象数据库ZODB的使用（python3经典编程案例）

以你之姓@ 2022-09-10 01:26 345阅读 0赞

## 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/][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 ###

## 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()

[http_www.zodb.org_en_latest]: http://www.zodb.org/en/latest/