Flask · Lesson 13 of 15

The Flask CLI and Shell

Custom flask commands, the shell context and one-off scripts.

Advanced
12 min read
3 objectives

Before this lessonLesson 12: Caching and Background Jobs

What you will learn

Add a CLI command
Expose models to flask shell
Run a seed script

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The flask command is the right place for one-off admin tasks: seed data, create an admin, print stats.

A custom command

import click
from flask.cli import with_appcontext

@click.command("seed")
@with_appcontext
def seed():
    if User.query.filter_by(email="ada@example.com").first():
        click.echo("already seeded")
        return
    u = User(email="ada@example.com")
    u.set_password("change-me")
    db.session.add(u)
    db.session.commit()
    click.echo("seeded ada")

def create_app():
    app = Flask(__name__)
    ...
    app.cli.add_command(seed)
    return app

flask --app myapp seed

Shell context

@app.shell_context_processor
def extras():
    return {"db": db, "User": User, "Post": Post}
# flask shell  ->  User.query.count()

Up next · Lesson 14Migrations and Schema ChangesExpand/contract migrations, data migrations and zero-downtime habits.