erlachemy_schemadisplay_anywidget_magic

IPython magic to generate a database schema using eralchemy and display it using jupyter_anywidget_graphviz Graphviz WASM anywidget.

Install from PyPi as:

pip install erlachemy_schemadisplay_anywidget_magic

Enable magics: %load_ext eralchemy_schemadisplay_magic

Create magic with "hidden" graphviz anywidget: %schema_magic_init

Alternatively, create an anywidget and pass it it:

from jupyter_anywidget_graphviz import (
    graphviz_headless,
)

g = graphviz_headless()
%schema_magic_init g

Create example database:

import sqlite3


def create_database():
    # Connect to (or create) the SQLite database
    conn = sqlite3.connect("example.db")
    cursor = conn.cursor()

    # Create the parent table
    cursor.execute(
        """
        CREATE TABLE IF NOT EXISTS users (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            name TEXT NOT NULL
        )
    """
    )

    # Create the child table with a foreign key reference to users
    cursor.execute(
        """
        CREATE TABLE IF NOT EXISTS orders (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id INTEGER NOT NULL,
            product TEXT NOT NULL,
            FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
        )
    """
    )

    # Commit and close
    conn.commit()
    conn.close()

create_database()

Generate schema as dot script and render using graphviz widget:

__Note that this requires the -m / --mode to be set to dot, which it is by default, although we can also pass it explicitly.

dot_data = %schema_magic -c "sqlite:///example.db" -m dot

from IPython.display import SVG
SVG( g.render(dot_data)["svg"] )

If we pass a widget in to the magic, and we have a "full" anywidget running environment (not JupyterLite/pyodide), we can use the -e / --embed switch to return the dot diagram rendered as SVG (this will attempt to create/use an internally created graphviz widget). Alternatively, we can pass a grpahviz widget using the -w / --widget-name parameter.

%schema_magic -c "sqlite:///example.db" -m dot -e

%schema_magic -c "sqlite:///example.db" -m dot -w g

TO DO - fix things so it works in Marimo:

• remove IPython refs
• move function to create and render dot file out of magic and into a cleaner py api