Python Pymongo中如何使用变量选择数据库

通常我连接到Pymongo中的数据库，如下所示：

    # connect to the MongoDB
    connection = MongoClient("mongodb://127.0.0.1:27017")

    # connect to the database
    self.db = self.connection.my_database

# connect to the MongoDB
connection = MongoClient("mongodb://127.0.0.1:27017")

# connect to the database
a = 'my_database'
self.db = self.connection[a]

问题是，我的_数据库的名称总是更改。如何使用变量选择数据库？

基于此，我们可以这样做：

    # connect to the MongoDB
    connection = MongoClient("mongodb://127.0.0.1:27017")

    # connect to the database
    self.db = self.connection.my_database

# connect to the MongoDB
connection = MongoClient("mongodb://127.0.0.1:27017")

# connect to the database
a = 'my_database'
self.db = self.connection[a]

基于此，我们可以这样做：

    # connect to the MongoDB
    connection = MongoClient("mongodb://127.0.0.1:27017")

    # connect to the database
    self.db = self.connection.my_database

# connect to the MongoDB
connection = MongoClient("mongodb://127.0.0.1:27017")

# connect to the database
a = 'my_database'
self.db = self.connection[a]

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本例中的自我指代是什么？本例中的自我指代是什么？