Vendoring Packages: FastAPI + Jinja2 Example

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This is an example of a Python Worker that uses a built-in package (FastAPI) with a vendored package (Jinja2).

Adding Packages

Built-in packages can be selected from this list and added to your requirements.txt file. These can be used with no other explicit install step.

Vendored packages are added to your source files and need to be installed in a special manner. The Python Workers team plans to make this process automatic in the future, but for now, manual steps need to be taken.

Vendoring Packages

First, install Python3.12 and pip for Python 3.12.

Currently, other versions of Python will not work - use 3.12!

Then create a virtual environment and activate it from your shell:

python3.12 -m venv .venv
source .venv/bin/activate

Within our virtual environment, install the pyodide CLI:

.venv/bin/pip install pyodide-build
.venv/bin/pyodide venv .venv-pyodide

Next, add packages to your vendor.txt file. Here we'll add jinja2

jinja2

Lastly, add these packages to your source files at src/vendor. For any additional packages, re-run this command.

.venv-pyodide/bin/pip install -t src/vendor -r vendor.txt

Using Vendored packages

In your wrangler.toml, make the vendor directory available:

[[rules]]
globs = ["vendor/**"]
type = "Data"
fallthrough = true

Now, you can import and use the packages:

import jinja2
# ... etc ...

Developing and Deploying

To develop your Worker, run wrangler dev.

To deploy your Worker, run wrangler deploy.