What do I need in order to run FastHtml?

[renatodamas]

I'm trying to run this very simple code adapt from FastHTML By Example

from fasthtml.common import *

app = FastHTML()

@app.get("/")
def home():
    return H1('Hello, World')

serve()

And I get this error:

ERROR:    Error loading ASGI app. Attribute "app" not found in module "site".

I've tried passing app as serve(app=app), and I get another error:

Error loading ASGI app. Attribute "<fasthtml.core.FastHTML object at 0x78e7bb236a50>" not found in module "site".

I'm running it in a virtual env where I've just installed fasthtml. Here is the output of pip freeze:

$ pip freeze
anyio==4.9.0
apsw==3.49.1.0
apswutils==0.0.2
beautifulsoup4==4.13.3
certifi==2025.1.31
click==8.1.8
fastcore==1.8.1
fastlite==0.1.3
h11==0.14.0
httpcore==1.0.7
httptools==0.6.4
httpx==0.28.1
idna==3.10
itsdangerous==2.2.0
lxml==5.3.2
mistletoe==1.4.0
oauthlib==3.2.2
packaging==24.2
python-dateutil==2.9.0.post0
python-dotenv==1.1.0
python-fasthtml==0.12.12
python-multipart==0.0.20
PyYAML==6.0.2
six==1.17.0
sniffio==1.3.1
soupsieve==2.6
starlette==0.46.1
typing_extensions==4.13.2
uvicorn==0.34.0
uvloop==0.21.0
watchfiles==1.0.5
websockets==15.0.1

Appreciate any help.

[renatodamas]

I've made a new clone of my project repository and now it is working.