python - 在python中打开一个新数据库之前检查是否存在与数据库的连接

Question

import dataset

class db(object):
    _db_connection = None
    _db_cur = None

    def __init__(self):
        self._db_connection = dataset.connect(path_to_database)

    def __del__(self):
        self._db_connection.executable.close()

在上面的代码中，我创建了一个类来连接到 AWS 上的现有数据库。有没有一种方法可以检查连接是否已打开，如果是，则返回现有连接而不是打开新连接？

Answer 1

您可以为此使用描述符:

class DBConn(object):
    conn = None

    def __get__(self, instance, owner):
        if instance is None:
            return self
        if self.conn is None or self.conn.closed():
            # Since this is a class attribute, it is shared by all instances
            self.conn = dataset.connect(path_to_database)
        return self.conn

    def __delete__(self, instance):
        self.conn.executable.close()
        self.conn = None

然后将其用作属性:

class DB(object):
    connection = DBConn()

db = DB()
db.connection.do_something()  # Opens a new connections
other_db = DB()
other_db.connection.do_something_else()  # Reuses same connection
del db.connection  # Closes the connection
other_db.connection.another_thing()  # Reopens the connection