Build an Install Wizard

This tutorial walks you through building a multi-screen install wizard — the kind of interactive CLI you'd use for setting up a tool, configuring a service, or onboarding a user.

What you'll build

A three-screen wizard:

Welcome — greet the user, explain what happens next
Config — collect a project name, environment, and confirmation via form fields
Install — run the install saga, show a progress bar, display results

Prerequisites

2/3 complete

Milo installed
Python 3.14+
Read the Quickstart

Build the Wizard

Define the screens

Create three FlowScreens with templates and reducers

Each screen is aFlowScreenwith its own template and reducer:

from milo.flow import FlowScreen

welcome = FlowScreen("welcome", "welcome.kida", welcome_reducer)
config = FlowScreen("config", "config.kida", config_reducer)
install = FlowScreen("install", "install.kida", install_reducer)

Write the welcome reducer

Advance on Enter

The welcome screen advances to config when the user presses Enter:

def welcome_reducer(state, action):
    if state is None:
        return {"ready": False}
    if action.type == "@@KEY" and action.payload.name == "ENTER":
        return {**state, "ready": True, "submitted": True}
    return state

Write the config reducer

Use form_reducer for structured input

The config screen usesform_reducerto handle form fields:

from milo import FieldSpec, FieldType
from milo.form import form_reducer

config_specs = [
    FieldSpec("project", "Project name"),
    FieldSpec("env", "Environment", field_type=FieldType.SELECT,
              choices=("dev", "staging", "prod")),
    FieldSpec("confirm", "Proceed with install?",
              field_type=FieldType.CONFIRM),
]

def config_reducer(state, action):
    if state is None:
        return form_reducer({"specs": config_specs}, action)
    return form_reducer(state, action)

Write the install reducer and saga

Trigger side effects with ReducerResult

The install screen triggers a saga on entry and tracks progress:

from milo import ReducerResult, Call, Put, Delay, Action

def install_reducer(state, action):
    if state is None:
        return ReducerResult(
            {"progress": 0, "status": "installing", "log": []},
            sagas=(install_saga,),
        )
    if action.type == "PROGRESS":
        return {**state, "progress": action.payload}
    if action.type == "INSTALL_DONE":
        return {**state, "progress": 100, "status": "done",
                "log": action.payload}
    return state

def install_saga():
    for i in range(1, 11):
        yield Delay(0.3)
        yield Put(Action("PROGRESS", payload=i * 10))
    result = yield Call(run_install, ())
    yield Put(Action("INSTALL_DONE", payload=result))

Create the templates

Kida templates for each screen

{{ "Install Wizard" | bold }}
{{ "=" * 40 | fg("dim") }}

This wizard will set up your project.

Press ENTER to continue.

{% include "form.kida" %}

Uses the built-in form template.

{{ "Installing..." | bold }}

{% include "progress.kida" %}

{% for line in log %}
{{ line }}
{% end %}

{% if status == "done" %}
{{ "Done!" | fg("green") | bold }}
{% end %}

Wire it up

Chain screens and run

from milo import App

flow = welcome >> config >> install
app = App.from_flow(flow)
app.run()