This application is comprised of many of the most common usages of SQLAlchemy, thus showing how to manage complexity and engaging in real world examples. Using easy, common language, the authors teach you how to turn knowledge into usable work. Essential Sqlalchemy. Get Books. This application is comprised of many of the most common usages of SQLAlchemy, thus showing how to manage. Essential SQLAlchemy. Using real-world examples, this practical guide shows you how to build a simple database application with SQLAlchemy, and how to connect to multiple databases simultaneously with the.
SQLAlchemy has become increasingly popular since its release, but it still lacks good offline documentation. This practical book fills the gap, and because. Die aktualisierte 2. These DBAPIs provide the basis for the dialect each database server speaks, and often enable the unique features seen in different database servers and versions.
While there are multiple DBAPIs available for many of the databases, the following instructions focus on the most common:. Psycopg2 provides wide support for PostgreSQL versions and features and can be installed with pip install psycopg2.
It can be installed with a pip install pymysql. Creating an additional dialect is well supported by SQLAlchemy, and Chapter 7 will examine the process of doing just that. To connect to a database, we need to create a SQLAlchemy engine. It does this by wrapping a pool of database connections and a dialect in such a way that they can work together to provide uniform access to the backend database.
SQLAlchemy provides a function to create an engine for us given a connection string and optionally some additional keyword arguments. A connection string is a specially formatted string that provides:. SQLite database connections strings have us represent a specific file or a storage location. Example P-1 defines a SQLite database file named cookies. This is because I prefer to be explicit instead of implicit, as recommended in the Zen of Python. By default, MySQL closes connections idle for more than eight hours.
This will log the actions processed by the engine, such as SQL statements and their parameters. It defaults to false. This defines the string encoding used by SQLAlchemy. This does not define the encoding type used by the backend database itself. This instructs SQLAlchemy to use a specific isolation level. This functions the same as doing it via a key-value pair in the connection string in dialects such as Psycopg2 that support that method. This recycles or times out the database connections at regular intervals.
This is important for MySQL due to the connection timeouts we mentioned earlier. It defaults to -1 , which means there is no timeout. Once we have an engine initialized, we are ready to actually open a connection to the database. That is done by calling the connect method on the engine as shown here:. Skip to main content. Start your free trial. If you want to view your data in a more schema-centric view as used in SQL , use Core.
If you have data for which business objects are not needed, use Core. If you view your data as business objects, use ORM. If you are building a quick prototype, use ORM. Optional authentication details username and password Location of the database file or hostname of the database server Optional database server port Optional database name SQLite database connections strings have us represent a specific file or a storage location.
Example P
0コメント