Python Pack

ASW-styled error pages and directory listings for Python web servers — drop-in support for http.server, Flask, and FastAPI.

Two tools, one pattern

The Python pack provides styled error responses for two different scenarios:

Both inline ASW styles by default — no external dependencies.

Dev server

packs/python/asw_server.py replaces python -m http.server with styled error pages and directory listings.

# Copy to your project
cp path/to/packs/python/asw_server.py .

# Run
python asw_server.py              # port 8000
python asw_server.py 3000         # custom port
python asw_server.py 3000 /dir    # custom port + directory

The server tries consecutive ports if the requested one is busy — useful for running multiple services in development.

What changes

• Error pages — 403, 404, 500 and all other HTTP errors show styled cards instead of the browser default
• Directory listings — a clean table replaces the raw <pre> autoindex
• Auto port fallback — if 8000 is busy, tries 8001, 8002, … up to 10 attempts
• No config required — drop the file in, run it

Flask/FastAPI error handlers

packs/flask/asw_errors.py registers error handlers on Flask or FastAPI applications with a single call.

Flask

from flask import Flask
from asw_errors import register_asw_errors

app = Flask(__name__)
register_asw_errors(app)

FastAPI

from fastapi import FastAPI
from asw_errors import register_asw_errors

app = FastAPI()
register_asw_errors(app)

register_asw_errors() auto-detects the framework from the app type. No conditional imports in your code.

Error codes covered

For FastAPI, RequestValidationError (the 422 raised by Pydantic) is registered separately in addition to HTTPException.

Linking agentic.css

By default, all styles are inlined — the page works with no external requests. If your app already serves agentic.css, link it instead to get custom fonts and the full theme:

register_asw_errors(app, css_url="/static/agentic.css")

Custom app name

The nav bar shows the app name. Flask auto-reads app.name; FastAPI reads app.title. Override either:

register_asw_errors(app, app_name="Mission Control")

Standalone HTML generation

The error_html() function is exported if you need to generate pages without registering handlers:

from asw_errors import error_html

# In a custom exception handler
body = error_html(404, path=request.path)
body = error_html(503, css_url="/static/agentic.css", app_name="My API")

Lazy imports

Flask and FastAPI are imported inside register_asw_errors(), not at module level. A project can import asw_errors.py with either framework installed — you won't get an ImportError for the other one.

Files

packs/python/
├── asw_server.py   http.server replacement with styled errors + directory listings
└── README.md       Dev server reference

packs/flask/
├── asw_errors.py   Flask + FastAPI error handler registration
└── README.md       Error pack reference