Chapter 2:
Connect your Python script to Anvil

We’re going to build a simple web UI to display the contents of our database in a table.

Step 1: Create an app

Log in to Anvil and click ‘New Blank App’. Choose the Material Design theme.

Location of the Create App button

Step 2: Add a Data Grid to your app

We’re going to add the interactive table that will contain the data from your external database.

Drag-and-drop a Data Grid Icon that looks like a table into your app:

Click on the Data Grid and go to ‘columns’ in the Properties Pane on the right.

Make the Data Grid have two columns:

  • Title: Name, Key: name
  • Title: Quantity, Key: quantity

Now your app is ready to display your data.

Step 5: Connect your script

At the top of your script, import the Anvil Uplink library:

# Import the Anvil Uplink library
import anvil.server

Below your import statements, run this line to connect to your script to your Anvil app. Replace <your-uplink-key> with the key shown in the Uplink dialog in step 3.

# Connect to your Anvil app
anvil.server.connect('<your uplink key>')

Add @anvil.server.callable to the line above your get_items function. This makes it possible to call this function from your Anvil app.

@anvil.server.callable
def get_items():
  # ... etc ...

Finally, add this line to the end - it keeps the script alive waiting for connections from your app:

# Wait for connections
anvil.server.wait_forever()

(Also, remove the print(get_items()) from the end of the script)

Your full script should now look like this:

import anvil.server
import psycopg2

anvil.server.connect('<your uplink key>')

conn = psycopg2.connect(
  host="35.177.174.19",
  user="your_database_id",
  password="your_database_password")
conn.set_session(autocommit=True)

cur = conn.cursor()

@anvil.server.callable
def get_items():
  cur.execute('SELECT * FROM inventory;')
  items = cur.fetchall()
  return [
    {'id': item[0], 'name': item[1], 'quantity': item[2]}
    for item in items
  ]

anvil.server.wait_forever()

Now we have the Uplink part of the system done:

We&rsquo;ve set up the database and proxied to it using the Uplink.

We’ve set up the database and proxied to it using the Uplink.

Step 6: Display the items

Now we’ll call the get_items function from Anvil and display the result in the Data Grid.

First, run your inventory.py script. It will initialise and wait for connections from your app:

$ python3 inventory.py
Connecting to wss://anvil.works/uplink
Anvil websocket open
Authenticated OK

In your Anvil app, go to the Code View of Form1.

At the end of the __init__ method, add this line:

    self.repeating_panel_1.items = anvil.server.call('get_items')

Now run your app. The data from your external Postgres database will be displayed in the table!

That’s every element of the system in place!

We&rsquo;ve implemented the whole system: the database, Uplink script, and web app.

We’ve implemented the whole system: the database, Uplink script, and web app.

Mission complete! That’s the essential task of this tutorial finished. We’ve connected to an external database and displayed its data in a web app.

In the next chapter, we’ll make it interactive: we’ll add, update and remove rows from the table from using the web UI.

Chapter complete

Congratulations, you've completed this chapter!