shelve:对象持久化的保存的模块，将对象保存到文件里 (默认的数据存储文件为二进制)，可持久化任何pickle可支持的Python数据格式

shelve 中唯一的方法：

shelve.open(filename,flag = 'c', protocol = None , writebake = False)

1. 文件可以像字典一样存储key - value (注：key 必须为字符串，value 可以是任何数据类型）

import shelve
date = shelve.open('family.txt') # Python的自处理系统会自动生成三个文件
date['father'] = 'Presly' # 默认为创建并且写入“c”
date['mather'] = 'Vera'
date['baby'] = [123, ]
date.close()
m = shelve.open('family.txt', falg= 'r', writebake=True) # 当writebake设置为True时，文件里才能直接添加
print(m['baby']) 
m['baby'].append(345)
print(m['father'])
print('-------------') 
for key, value in m.items(): # 以字典的格式 
 print(key, ':', value) 
m.close()

[123]
Presly
-------------
father : Presly
mather : Vera
baby : [123，345]

2. shelve 的序列化

3. shelve 可以进行类似于库，增，删，改，查

import shelve


def store_information(database):
 info = {}
 ID = input('Enter the ID number:')
 info['name'] = input('Enter the name:') # 将name ,age , phone 存入字典info里
 info['age'] = input('Enter the age:')
 info['phone'] = input('Enter the phone:')
 database[ID] = info # 用ID ： info 存入 database文件


def lookup_information(database):
 ID = input('Enter the ID:')
 field = input('What would you like to know?(name,age,phone)')
 field = field.strip().lower()
 print(database[ID][field]) # 通过输入的ID与 field 直接打印结果


def print_help():
 print('Please enter the help command:')
 print('store :store informatinon to database')
 print('lookup :look up information by numID')
 print('quit :save information and quit')
 print('? :print help command')


def enter_command():
 cmd = input('Enter command (? for help)')
 cmd = cmd.strip().lower()
 return cmd


def main():
 database = shelve.open('db.dat')
 try:
 while True:
 cmd = enter_command()
 if cmd == 'store':
 store_information(database) # 当if函数结束，自动跳转到cmd = enter_command()行
 elif cmd == 'lookup':
 lookup_information(database)
 elif cmd == '?':
 print_help()
 elif cmd == 'quit':
 return # 跳出while循环
 finally:
 database.close()


if __name__ == '__main__': main()