How to Download Files with FastAPI: A Complete Tutorial

File management is a critical feature for many modern applications. Whether you’re delivering documents, software, or data files, a robust file download endpoint is essential. In this blog, we’ll show you how to create a file download API using FASTAPI that delivers files dynamically based on client requests.

Prerequisites

Before diving in, ensure you have the following:

1. Python Installed: Version 3.7 or above.
2. FastAPI Installed: You can install it using pip: pip install fastapi
3. Files to Serve: Ensure the directory structure contains files for testing (e.g., ‘C:\ModelStorage’)

Setting Up the Endpoint

Here’s the code to build a file download endpoint:

from fastapi import FastAPI
from fastapi.responses import FileResponse
app = FastAPI()
@app.get("/downloadfile/")
async def download_file(asset: str, file_path: str):
   """
   Endpoint to download a file from the server.
   :param asset: Subdirectory under the base directory.
   :param file_path: Name of the file to download.
   :return: File as a downloadable response.
   """
   # Construct the full file path
   model_file_path = f"C:\\ModelStorage\\{asset}\\{file_path}"
  # Return the file as a response
   return FileResponse(model_file_path, media_type="application/octet-stream", filename=file_path)

Code Breakdown