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Introduction

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.8+ based on standard Python type hints.

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Prerequisites

  • a UNIX-like system (see WSL if you are using Windows), in order to use the Valyent CLI
  • a Valyent account, with a registered payment method (you can sign up here)
  • Python3 and installed on your machine

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Installing the CLI

curl -L https://cli.valyent.cloud | sh
You can inspect the installation script here and the GitHub repository.

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Authenticating

valyent auth login

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Initializing the project

In the first place, we are going to install FastAPI dependencies. You can refer to the official documentation for more information. 
pip install "fastapi[standard]"
Then, we can scaffold a new FastAPI project : 
mkdir fastapi-app && cd fastapi-app && touch main.py
Make sure to create a requirements.txt file, in order to install the dependencies in the Docker image : 
pip freeze > requirements.txt
In the main.py file, we can add the following code : 
# main.py
from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
  return {"Hello": "World"}
Now, we can initialize the valyent.toml configuration file, that allows to link the local codebase, to a Valyent application : 
valyent init
This command will ask you to select/create a project and an associated application.

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Adding the Dockerfile

Let’s add a Dockerfile so that Valyent can build a Docker image for your application. 
touch Dockerfile
We can fill it with the following Dockerfile (coming from here) : 
# Stage 1: Builder
FROM python:3.13 AS builder

WORKDIR /code

# Install dependencies
COPY ./requirements.txt /code/requirements.txt
RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt

# Stage 2: Runtime
FROM python:3.13-slim AS runtime

WORKDIR /code

# Copy only necessary files from the builder stage
COPY --from=builder /usr/local/lib/python3.13/site-packages /usr/local/lib/python3.13/site-packages
COPY --from=builder /usr/local/bin /usr/local/bin

# Copy the application code
COPY ./ /code/

CMD ["fastapi", "run", "--host", "0.0.0.0", "--port", "80"]

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Deploy the project

To expose the application’s port, we need to set up a gateway (in this case, the port 80): 
valyent gateways create
Then, we can deploy the application : 
valyent deploy
Then, you can type the following: 
valyent open
to test your FastAPI application in your browser.