Using databases

– OK, what if I need to use a database in my application?
you can use the included ORM

weppy comes with an integrated ORM based on pyDAL, which gives you the ability to use a database in your application writing simple Python code without worrying about queries and specific syntax of the database engine you want to use.

Thanks to this database layer, you can write the same code and use the same syntax independently of which of the available adapters you want to use during development or when you're deploying your app to the world.

This is the list of the supported database engines, where we included the appropriate driver(s) you need to install, separately from weppy (just use pip):

Supported DBMS python driver(s)
SQLite sqlite3, pysqlite2, zxjdbc
PostgreSQL psycopg2, pg8000, zxjdbc
MySQL pymysql, mysqldb
Oracle cxoracle
MSSQL pyodbc
FireBird kinterbasdb, fdb, pyodbc
DB2 pyodbc
Informix informixdb
Ingres ingresdbi
Cubrid cubridb
Sybase Sybase
Teradata pyodbc
SAPDB sapdb
MongoDB pymongo

This list may change, and depends on the engine support of pyDAL. For any further information, please check out the project page.

So, how do you use weppy's ORM? Let's see it with an example:

from weppy import App
from weppy.dal import DAL, Model, Field

app = App(__name__)
app.config.db.uri = "sqlite://storage.sqlite"

class Post(Model):
    author = Field()
    title = Field()
    body = Field('text')

db = DAL(app)

app.common_handlers = [db.handler]

def post_by(author):
    posts = db( == author).select()
    return dict(posts=posts)

The above code is quite simple: the post_by() function lists posts from a specific author. Let's retrace what we done in those simple lines:

  • we added an sqlite database to our application, stored on file storage.sqlite
  • we defined the Post model and its properties, which will create a posts table
  • we registered the database handler to our application so that it will be available during requests
  • we did a select on the posts table querying the author column

As you noticed, the fields defined for the table are available for queries as attributes, and calling db with a query argument provides you a set on which you can do operations like the select().

In the next chapters, we will inspect how to define models, all the available options, and how to use weppy's ORM to perform operations on the database.