Connect Streamlit to PostgreSQL

Introduction

This guide explains how to securely access a remote PostgreSQL database from Streamlit Community Cloud. It uses st.connection and Streamlit's Secrets management. The below example code will only work on Streamlit version >= 1.28, when st.connection was added.

Create a PostgreSQL database

First, follow this tutorial to install PostgreSQL and create a database (note down the database name, username, and password!). Open the SQL Shell (psql) and enter the following two commands to create a table with some example values:

CREATE TABLE mytable (
    name            varchar(80),
    pet             varchar(80)
);

INSERT INTO mytable VALUES ('Mary', 'dog'), ('John', 'cat'), ('Robert', 'bird');

Add username and password to your local app secrets

Your local Streamlit app will read secrets from a file .streamlit/secrets.toml in your app's root directory. Create this file if it doesn't exist yet and add the name, user, and password of your database as shown below:

# .streamlit/secrets.toml

[connections.postgresql]
dialect = "postgresql"
host = "localhost"
port = "5432"
database = "xxx"
username = "xxx"
password = "xxx"

Copy your app secrets to the cloud

As the secrets.toml file above is not committed to GitHub, you need to pass its content to your deployed app (on Streamlit Community Cloud) separately. Go to the app dashboard and in the app's dropdown menu, click on Edit Secrets. Copy the content of secrets.toml into the text area. More information is available at Secrets management.

Add dependencies to your requirements file

Add the psycopg2-binary and SQLAlchemy packages to your requirements.txt file, preferably pinning its version (replace x.x.x with the version you want installed):

# requirements.txt
psycopg2-binary==x.x.x
sqlalchemy==x.x.x

Write your Streamlit app

Copy the code below to your Streamlit app and run it. Make sure to adapt query to use the name of your table.

# streamlit_app.py

import streamlit as st

# Initialize connection.
conn = st.connection("postgresql", type="sql")

# Perform query.
df = conn.query('SELECT * FROM mytable;', ttl="10m")

# Print results.
for row in df.itertuples():
    st.write(f"{row.name} has a :{row.pet}:")

See st.connection above? This handles secrets retrieval, setup, query caching and retries. By default, query() results are cached without expiring. In this case, we set ttl="10m" to ensure the query result is cached for no longer than 10 minutes. You can also set ttl=0 to disable caching. Learn more in Caching.

If everything worked out (and you used the example table we created above), your app should look like this: