--- title: "💭 Automatic browser reloading in FastAPI" description: "!https://gist.github.com/vrslev/6d0602bfa939a01844f645c608afb85a" date: 2023-10-08 published: true tags: - webdev - fastapi - thought template: link ---
main.py python 
import os

import arel
from fastapi import FastAPI, Request
from fastapi.templating import Jinja2Templates

app = FastAPI()
templates = Jinja2Templates("templates")

if _debug := os.getenv("DEBUG"):
    hot_reload = arel.HotReload(paths=[arel.Path(".")])
    app.add_websocket_route("/hot-reload", route=hot_reload, name="hot-reload")
    app.add_event_handler("startup", hot_reload.startup)
    app.add_event_handler("shutdown", hot_reload.shutdown)
    templates.env.globals["DEBUG"] = _debug
    templates.env.globals["hot_reload"] = hot_reload


@app.get("/")
def index(request: Request):
    return templates.TemplateResponse("index.html", context={"request": request})

# run:
# DEBUG=true uvicorn main:app --reload
I just discovered [arel](https://pypi.org/project/arel/) for hot reloading python applications when content changes from this snippet that implements it for fatapi. On app startup add the `/hot-reload` routes if in **DEBUG** mode. ``` python import os import arel from fastapi import FastAPI, Request from fastapi.templating import Jinja2Templates app = FastAPI() templates = Jinja2Templates("templates") if _debug := os.getenv("DEBUG"): hot_reload = arel.HotReload(paths=[arel.Path(".")]) app.add_websocket_route("/hot-reload", route=hot_reload, name="hot-reload") app.add_event_handler("startup", hot_reload.startup) app.add_event_handler("shutdown", hot_reload.shutdown) templates.env.globals["DEBUG"] = _debug templates.env.globals["hot_reload"] = hot_reload @app.get("/") def index(request: Request): return templates.TemplateResponse("index.html", context={"request": request}) # run: # DEBUG=true uvicorn main:app --reload ``` install `arel` and make sure you have `uvicorn[standard]` for websocket support. ``` text fastapi uvicorn[standard] arel jinja2 ``` In the template, load the script when in debug mode. ``` html {% block content %}{% endblock %} {% if DEBUG %} {{ hot_reload.script(url_for('hot-reload')) | safe }} {% endif %} ``` !!! note This post is a thought. It's a short note that I make about someone else's content online #thoughts