函数一个用法

'''
handle all the database interactions
'''
import json, time, os
from  conf import settings


def file_db_handle(conn_params):
    '''
    parse the db file path
    :param conn_params: the db connection params set in settings
    :return:
    '''
    print('file db:', conn_params)
    # db_path ='%s/%s' %(conn_params['path'],conn_params['name'])
    return file_execute  #3返回给外部程序，一个函数名。外部程序就可以进行调用，这个函数


def db_handler():  #1外部程序最先调用这个
    '''
    connect to db
    :param conn_parms: the db connection params set in settings
    :return:a
    '''
    conn_params = settings.DATABASE
    if conn_params['engine'] == 'file_storage':
        return file_db_handle(conn_params)  #2返回值是另一个函数的执行结果
    elif conn_params['engine'] == 'mysql':
        pass  # todo


def file_execute(sql, **kwargs):
    """
    对sql语句进行解析并执行
    :param sql:  eg. select * from accounts where account=1344
    :param kwargs: 
    :return: 
    """
    conn_params = settings.DATABASE
    db_path = '%s/%s' % (conn_params['path'], conn_params['name'])

    print(sql, db_path)
    sql_list = sql.split("where")
    print(sql_list)
    if sql_list[0].startswith("select") and len(sql_list) > 1:  # has where clause
        column, val = sql_list[1].strip().split("=")

        if column == 'account':
            account_file = "%s/%s.json" % (db_path, val)
            print(account_file)
            if os.path.isfile(account_file):
                with open(account_file, 'r') as f:
                    account_data = json.load(f)
                    return account_data
            else:
                exit("33[31;1mAccount [%s] does not exist!33[0m" % val)

    elif sql_list[0].startswith("update") and len(sql_list) > 1:  # has where clause
        column, val = sql_list[1].strip().split("=")
        if column == 'account':
            account_file = "%s/%s.json" % (db_path, val)
            # print(account_file)
            if os.path.isfile(account_file):
                account_data = kwargs.get("account_data")
                with open(account_file, 'w') as f:
                    acc_data = json.dump(account_data, f)
                return True