Serve a dynamic SVG badge

In this example, we use Modal’s webhook capability to host a dynamic SVG badge that shows you the current # of downloads for a Python package.

First let’s start off by creating a Modal stub, and defining an image with the Python packages we’re going to be using:

import modal

stub = modal.Stub(
    "example-web-badges",
    image=modal.Image.debian_slim().pip_install("pybadges", "pypistats"),
)

Defining the webhook

Instead of using @stub.function to decorate our function, we use the @modal.webhook decorator (learn more), which instructs Modal to create a REST endpoint that serves this function. Note that the default method is GET, but this can be overridden using the method argument.

@stub.webhook
async def package_downloads(package_name: str):
    import json

    import pypistats
    from fastapi import Response
    from pybadges import badge

    stats = json.loads(pypistats.recent(package_name, format="json"))
    svg = badge(
        left_text=f"{package_name} downloads",
        right_text=str(stats["data"]["last_month"]),
        right_color="blue",
    )

    return Response(content=svg, media_type="image/svg+xml")

In this function, we use pypistats to query the most recent stats for our package, and then use that as the text for a SVG badge, rendered using pybadges. Since Modal webhooks are FastAPI functions under the hood, we return this SVG wrapped in a FastAPI response with the correct media type. Also note that FastAPI automatically interprets package_name as a query param.

Running and deploying

We can now run an ephemeral app on the command line using:

modal serve badges.py

This will create a short-lived web url that exists until you terminate the script. It will also hot-reload the code if you make changes to it.

If you want to create a persistent URL, you have to deploy the script. To deploy using the Modal CLI by running modal deploy badges.py,

Either way, as soon as we run this command, Modal gives us the link to our brand new webhook in the output:

web badge deployment

We can now visit the link using a web browser, using a package_name of our choice in the URL query params. For example:

  • https://YOUR_SUBDOMAIN.modal.run/?package_name=synchronicity
  • https://YOUR_SUBDOMAIN.modal.run/?package_name=torch

Try this on Modal!

You can run this on Modal with 60 seconds of work!
Creating an account is free and no credit card is required. After creating an account, install the Modal Python package and create an API token:
pip install modal-client
modal token new
git clone https://github.com/modal-labs/modal-examples
cd modal-examples
modal run 07_webhooks/badges.py