Quickstart: Server Code

Learn how to run code in Anvil’s hosted Python backend

Anvil provides a server-side Python environment for your apps.

Follow this quickstart to write a server function and call it from the client.

Add a Server Module

In the App Browser, click the + next to Server Code to add a new Server Module.

Adding a Server Module in the App Browser

You will see a code editor with a yellow background.

In the App Browser, click “+ Add Server Module” next to Server Code to add a new Server Module.

A new tab will open with a code editor. The orange line on the left margin of the code editor indicates that this code will run on the server.

Python server code with an orange background

Write a server function

Write this function into the Server Module:

def say_hello(name):
  print(f"Hello from the server, {name}")
  return [1, 2, 3, 4]

Make your function client-callable

Above your say_hello function, add @anvil.server.callable. The function now looks like this:

@anvil.server.callable
def say_hello(name):
  print(f"Hello from the server, {name}")
  return [1, 2, 3, 4]

That makes the say_hello function callable from the client side.

Switch to the Code View for Form1

Under Forms in the App Browser, select Form1.

Click on the ‘Code’ tab to see the Python code for Form1.

The Design View for Form1 with the Code tab in the top-right highlighted

Call your server function from the client

You will see a few lines of pre-written code. Your Form is represented as a class called Form1. It currently has only one method, the __init__ method.

At the end of the __init__ method, write these lines:

    return_value = anvil.server.call('say_hello', 'Anvil Developer')
    print(f"The return value was {return_value}")

Run your app

Now click the ‘Run’ button at the top of the screen.

The Output Panel should display these lines:

The Output Panel showing printed messages with yellow and white backgrounds

The output with the yellow background came from a Python process running in Anvil’s cloud cluster. The output with the white background ran in your browser. You made the browser communicate with the server over the internet by writing anvil.server.call('say_hello', 'Anvil Developer').

The Output Panel showing printed messages from the client and server

The output with the orange line next to it came from a Python process running in Anvil’s cloud cluster. The output with the blue line next to it ran in your browser. You made the browser communicate with the server over the internet by writing anvil.server.call('say_hello', 'Anvil Developer').