fast-dash

Turn any Python function into a web app with a single decorator ⚡

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• Documentation: docs.fastdash.app
• Source: github.com/dkedar7/fast_dash
• Install: pip install fast-dash
• Claude Code users: /plugin marketplace add dkedar7/fast_dash then /plugin install fast-dash@fast-dash to load the Fast Dash skill — agents will pick it up automatically when you ask them to "turn this function into a web app".

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What is Fast Dash?

Fast Dash inspects your Python function's signature, picks UI components from the type hints and default values, and serves the result as a Plotly Dash app — usually in under five lines of code. No frontend, no callbacks, no boilerplate.

It exists for one job: collapse the gap between a working Python function and a shareable interactive web app.

30-second example

pip install fast-dash

from fast_dash import fastdash

@fastdash
def greet(name: str = "world") -> str:
    return f"Hello, {name}!"

# Serving on http://127.0.0.1:8080

That's the entire app. Open the URL, type a name, click Run, see the response.

How it works

The @fastdash decorator does three things at import time:

1. Inspects the function signature — each parameter becomes an input component, the return becomes an output component.
2. Picks components from type hints and defaults — int → number input, bool → checkbox, pd.DataFrame → table, etc. (full table below).
3. Builds a Dash app and starts the server — the function body is wired as the callback that runs when the user clicks Run.

You can override any of this by passing components explicitly via inputs= and outputs=, or by skipping the decorator and using the FastDash(...) class directly.

Type hint → component reference

Inputs (parameter type → UI component):

Type hint	Component
str	Textarea
str with default=[...]	Single-select dropdown
int, float	Number input
int/float with range(...) default	Slider
bool	Checkbox
list	Multi-select dropdown
dict (with default)	Multi-select dropdown (keys)
datetime.date	Date picker
PIL.Image.Image	Image upload
Literal["a", "b"]	Single-select dropdown
enum.Enum subclass	Single-select dropdown
Annotated[int, range(0, 100)]	Slider
Annotated[str, ["a", "b"]]	Single-select dropdown
Optional[T]	As T, but nullable
Any Dash component instance	Used directly
Any Fast Dash component (Text, Slider, ...)	Used directly

Outputs (return type → UI component):

Return type	Component
str, int, float, etc.	Text (rendered as <h1>)
pd.DataFrame	Table
PIL.Image.Image, matplotlib.figure.Figure	Image
plotly.graph_objects.Figure (or string-form "go.Figure", "Figure")	Plotly chart
Tuple of types	Multiple outputs (one component each)
Any Fast Dash component (Graph, Image, ...)	Used directly

from fast_dash import fastdash, Graph

@fastdash
def chart(rows: int = 100) -> Graph:
    import plotly.express as px
    return px.scatter(px.data.iris().head(rows), x="sepal_width", y="sepal_length")

Unknown hints fall back to text. Source-introspection failures (REPL, exec) fall back to generic OUTPUT_1, OUTPUT_2 labels — the app still works.

Built-in components