如何通过 Python 中的 YAML 配置文件检查与数据库的连接？

我有项目需要一个 YAML 配置文件来检查与数据库的连接，我有一些问题：如果特定于主机的没有，它将自动成为默认值（本地主机）。我已经用示例文件对其进行了测试

下面，但似乎我的代码有问题，主机在为空时不会将默认值显示为 loacalhost ，否则不显示。任何人都可以给我建议吗？我哪里错了？

我的示例文件 data_source.yml：

database: 

dbopt:
   host: 
   port: 5432
   dbname: db1
   user: username
   password: 1234
   client_encoding: utf-8
   connect_timeout: 60
   sslmode: none

query:
   select * from manufacturing_product

query:
   select * from manufacturing_product

我的代码：

import yaml

class InvalidConfigError(Exception):
    pass

class DB:
    def __init__(self, dbconf):
        self._dbconf = dict(dbconf)

        # checking for database type
        dbtype = self.get_db_type()
        if dbtype != 'sqlite' and dbtype != 'postgres':
            raise InvalidConfigError(
                'E01001', 'Invalid database type, should be sqlite or postgres.')
        else:
            self.dbtype = dbtype

        #checking db option
        dbopt = self.__get_dbopt()
        if dbopt is None:
            raise InvalidConfigError(
                'E01002', 'Invalid database options.')
        else:
            self.dbopt = dbopt

        #checking host
        host = dbopt.get('host')
        if host is None or len(host) <= 0:
            self.host = 'localhost'
        else:
            self.host = host

        #checking dbname
        dbname = dbopt.get('dbname')
        if dbname is None or len(dbname) <= 0:
            raise Exception("Database name is required.")
        else:
            self.dbname = dbname

    def get_db_type(self):
        return self._dbconf['db']

    def __get_dbopt(self):
        return self._dbconf.get('dbopt')

    def get_db_host(self):
        return self.host

    def get_db_name(self):
        return self.dbname

with open('data_source.yml') as file:
    data = yaml.full_load(file)

    for item, doc in data.items():
        print(item, ":", doc)

    db = DB(data)

输出：

database: 

dbopt:
   host: 
   port: 5432
   dbname: db1
   user: username
   password: 1234
   client_encoding: utf-8
   connect_timeout: 60
   sslmode: none

query:
   select * from manufacturing_product