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Build a Python App with Reflex and Lakebase Postgres

Summary: Connecting a Reflex Python web app to Lakebase Postgres requires setting a DATABASE_URL in rxconfig.py via python-dotenv, defining sqlmodel ORM models, and running Alembic migrations. Use this page when building a Python full-stack application with Reflex that needs a serverless Postgres backend, covering virtual environment setup, psycopg2-binary installation, schema migrations, and a working CRUD example.

Build a Python App with Reflex and Lakebase Postgres

Section titled “Build a Python App with Reflex and Lakebase Postgres”

Learn how to build a Python Full Stack application with Reflex and Lakebase Postgres

Pre-built prompt for connecting Reflex applications to Lakebase Postgres View prompt

Reflex is a Python web framework that allows you to build full-stack applications with Python.

Using Reflex, you can build frontend and backend applications using Python to manage the interaction between the frontend UI and the state with the server-side logic. To make the application data-driven, you can connect to a Lakebase Postgres database.

To connect to a Lakebase Postgres database from a Reflex application:

Create a Neon project

Section titled “Create a Neon project”

If you do not have one already, create a Neon project. Save your connection details including your password. They are required when defining connection settings.

To create a Neon project:

  1. Navigate to the Projects page in the Neon Console.
  2. Click New Project.
  3. Specify your project settings and click Create Project.

Set up a Reflex project

Section titled “Set up a Reflex project”

To set up a Reflex project, you need to install the Reflex CLI and create a new project.

Create the project directory

Section titled “Create the project directory”

Create a new directory for your Reflex project and navigate to it:

Bash
mkdir with_reflex
cd with_reflex

Create a virtual environment

Section titled “Create a virtual environment”

It's recommended to use a virtual environment to manage your project dependencies. In this example, venv is used to create a virtual environment. You can use any other virtual environment manager of your choice like poetry, pipenv, or uv.

To create a virtual environment, run the following command in your project directory:

MacOS/Linux

Bash
python3 -m venv .venv
source .venv/bin/activate

Windows

Shell
py -3 -m venv .venv
.venv\Scripts\activate

Install the required packages

Section titled “Install the required packages”

Install Reflex, python-dotenv to manage environment variables, and psycopg2-binary to connect to Postgres:

Bash
pip install reflex python-dotenv psycopg2-binary

To initialize the Reflex app, run the following command:

Bash
reflex init

When prompted choose: A blank Reflex app (option 1). You should see output similar to the following:

Bash
$ reflex init
──────────────────────────────────────────── Initializing with_reflex ─────────────────────────────────────────────
[07:20:37] Initializing the web directory.                                                             console.py:231

Get started with a template:
(0) Try our free AI builder.
(1) A blank Reflex app.
(2) Premade templates built by the Reflex team.
Which template would you like to use? (0): 1
[07:20:39] Initializing the app directory.                                                             console.py:231
Success: Initialized with_reflex using the blank template.

When the project is initialized, Reflex CLI creates a project directory. This directory will contain the following files and directories:

with_reflex
├── .web
├── assets
├── with_reflex
│   ├── __init__.py
│   └── with_reflex.py
└── rxconfig.py

The rxconfig.py file contains the project configuration settings. This is where the database connection settings will be defined.

Configure Reflex connection settings

Section titled “Configure Reflex connection settings”

Now that you have set up a Reflex project, you can configure the connection settings to connect to Neon.

Create a .env file

Section titled “Create a .env file”

Create a .env file in the root of your project directory to store your Neon connection string. Add the following line to the .env file, replacing the placeholder values with your actual Neon connection details:

.env
DATABASE_URL="postgresql://<user>:<password>@<endpoint_hostname>.neon.tech:<port>/<dbname>?sslmode=require&channel_binding=require"

You can find the connection string for your database by clicking the Connect button in the Console nav. For more information, see Connect from any application.

Update the rxconfig.py file

Section titled “Update the rxconfig.py file”

  1. Open the rxconfig.py file in the project directory.

  2. Update the file to load the environment variables from the .env file and set the db_url parameter with the DATABASE_URL environment variable:

    Python
    import osfrom dotenv import load_dotenvimport reflex as rxload_dotenv()config = rx.Config(  app_name="with_reflex",  plugins=[     rx.plugins.SitemapPlugin(),     rx.plugins.TailwindV4Plugin(),  ],  db_url=os.environ.get("DATABASE_URL"))

  3. Save the changes to the rxconfig.py file.

    Now, you can run the Reflex app and start building your Python full-stack application with Reflex and Neon.

Creating a data model

Section titled “Creating a data model”

To create a data model in Reflex, you can define a Python class that represents the data structure. Reflex uses sqlmodel to provide a built-in ORM wrapping SQLAlchemy.

Add the following code to with_reflex/with_reflex.py to create a Customer model:

Python
"""Welcome to Reflex! This file outlines the steps to create a basic app."""import reflex as rxfrom rxconfig import configclass Customer(rx.Model, table=True):    """The customer model."""    name: str    email: str    phone: str    address: strclass State(rx.State):    """The app state."""def index() -> rx.Component:    # Welcome Page (Index)    return rx.container(        rx.color_mode.button(position="top-right"),        rx.vstack(            rx.heading("Welcome to Reflex!", size="9"),            rx.text(                "Get started by editing ",                rx.code(f"{config.app_name}/{config.app_name}.py"),                size="5",            ),            rx.link(                rx.button("Check out our docs!"),                href="https://reflex.dev/docs/getting-started/introduction/",                is_external=True,            ),            spacing="5",            justify="center",            min_height="85vh",        ),    )app = rx.App()app.add_page(index)

This code defines a Customer model with fields for name, email, phone, and address. The table=True argument tells Reflex to create a table in the database for this class.

Generate the Alembic migration files

Section titled “Generate the Alembic migration files”

Reflex uses Alembic to manage database migrations. To generate the Alembic migration files, run the following command in your project directory:

Bash
reflex db init

Create and apply the migration

Section titled “Create and apply the migration”

Run the following command to create a new migration file that reflects the changes made to the data model:

Bash
reflex db makemigrations --message 'create customer model'

After creating the migration file, apply the migration to the database by running:

Bash
reflex db migrate

This command applies the migration to the database, updating the schema to match the model definition.

You can verify that the customer table has been created in your Neon database by visiting the Tables section in the Neon Console.

Create the Reflex app

Section titled “Create the Reflex app”

Update the with_reflex/with_reflex.py file to create a simple Customer Data App that allows you to add and view customer records.

Python
"""Welcome to Reflex! This file outlines the steps to create a basic app."""

import reflex as rx
from rxconfig import config


class Customer(rx.Model, table=True):
    """The customer model."""

    name: str
    email: str
    phone: str
    address: str


class State(rx.State):
    """The app state."""

    # Form fields
    name: str = ""
    email: str = ""
    phone: str = ""
    address: str = ""

    # List of customers
    customers: list[Customer] = []

    def load_customers(self):
        """Load all customers from the database."""
        with rx.session() as session:
            self.customers = session.exec(Customer.select()).all()

    def add_customer(self):
        """Add a new customer to the database."""
        if self.name and self.email:
            with rx.session() as session:
                customer = Customer(
                    name=self.name,
                    email=self.email,
                    phone=self.phone,
                    address=self.address,
                )
                session.add(customer)
                session.commit()

            # Clear form fields
            self.name = ""
            self.email = ""
            self.phone = ""
            self.address = ""

            # Reload customers
            self.load_customers()

    def delete_customer(self, customer_id: int):
        """Delete a customer from the database."""
        with rx.session() as session:
            customer = session.get(Customer, customer_id)
            if customer:
                session.delete(customer)
                session.commit()

        # Reload customers
        self.load_customers()


def index() -> rx.Component:
    return rx.box(
        rx.color_mode.button(position="top-right"),
        rx.vstack(
            # Header
            rx.heading(
                "Customer Management",
                size="8",
                weight="bold",
                margin_bottom="2rem",
            ),
            # Add Customer Section
            rx.card(
                rx.vstack(
                    rx.heading("➕ Add New Customer", size="5", weight="medium"),
                    rx.grid(
                        rx.input(
                            placeholder="Name *",
                            value=State.name,
                            on_change=State.set_name,
                            size="3",
                        ),
                        rx.input(
                            placeholder="Email *",
                            value=State.email,
                            on_change=State.set_email,
                            size="3",
                        ),
                        rx.input(
                            placeholder="Phone",
                            value=State.phone,
                            on_change=State.set_phone,
                            size="3",
                        ),
                        rx.input(
                            placeholder="Address",
                            value=State.address,
                            on_change=State.set_address,
                            size="3",
                        ),
                        columns="4",
                        spacing="4",
                        width="100%",
                    ),
                    rx.button(
                        "Add Customer",
                        on_click=State.add_customer,
                        size="3",
                        variant="solid",
                        color_scheme="blue",
                        width="auto",
                    ),
                    spacing="4",
                    width="100%",
                ),
                size="3",
                width="100%",
            ),
            # Spreadsheet Table
            rx.card(
                rx.vstack(
                    rx.heading(
                        f"📊 Customer List ({State.customers.length()} total)",
                        size="5",
                        weight="medium",
                    ),
                    rx.box(
                        rx.table.root(
                            rx.table.header(
                                rx.table.row(
                                    rx.table.column_header_cell("ID", width="80px"),
                                    rx.table.column_header_cell("Name"),
                                    rx.table.column_header_cell("Email"),
                                    rx.table.column_header_cell("Phone"),
                                    rx.table.column_header_cell("Address"),
                                    rx.table.column_header_cell(
                                        "Actions", width="120px"
                                    ),
                                ),
                            ),
                            rx.table.body(
                                rx.foreach(
                                    State.customers,
                                    lambda customer, index: rx.table.row(
                                        rx.table.cell(
                                            rx.badge(
                                                customer.id,
                                                color_scheme="gray",
                                                variant="soft",
                                            ),
                                        ),
                                        rx.table.cell(
                                            rx.text(customer.name, weight="medium"),
                                        ),
                                        rx.table.cell(
                                            rx.text(customer.email),
                                        ),
                                        rx.table.cell(
                                            rx.text(customer.phone),
                                        ),
                                        rx.table.cell(
                                            rx.text(customer.address),
                                        ),
                                        rx.table.cell(
                                            rx.button(
                                                rx.icon("trash-2", size=16),
                                                on_click=lambda: State.delete_customer(
                                                    customer.id
                                                ),
                                                size="2",
                                                variant="soft",
                                                color_scheme="red",
                                            ),
                                        ),
                                        align="center",
                                    ),
                                ),
                            ),
                            variant="surface",
                            size="3",
                            width="100%",
                        ),
                        width="100%",
                        overflow_x="auto",
                    ),
                    spacing="4",
                    width="100%",
                ),
                size="3",
                width="100%",
            ),
            spacing="6",
            width="100%",
            max_width="1400px",
            padding="2rem",
        ),
        width="100%",
        display="flex",
        justify_content="center",
        min_height="100vh",
        background="var(--gray-1)",
        on_mount=State.load_customers,
    )


app = rx.App()
app.add_page(index)

The following features are included in this Customer Data App:

  • Add new customers with name, email, phone, and address.
  • View a list of all customers in a table format.
  • Delete customers from the list.

Run the Reflex app

Section titled “Run the Reflex app”

To run the Reflex app, use the following command in your project directory:

Bash
reflex run

This command starts the Reflex development server. You can access the app by navigating to http://localhost:3000 in your web browser.

You should see the Customer Data App interface, where you can add, view, and delete customer records stored in your database.

Reflex Customer Data App

Next steps

Section titled “Next steps”
Section titled “Related docs (Frameworks)”

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