curriculum/1.solar-system/3.strings/03.the-methods/index.md

type, title, xp, duration, difficulty

type	title	xp	duration	difficulty
challenge	The Methods	50	30	2

The Methods

[INCOMING — Mission Control, Earth]

Cadet, every string carries a toolkit of methods. The most-used:

• s.upper() — uppercase copy
• s.lower() — lowercase copy
• s.strip() — drops leading/trailing whitespace
• s.replace(a, b) — every a becomes b

Methods can be chained — each returns a new string you can call the next on:

"  Hello World  ".strip().lower().replace(" ", "_")
# → "hello_world"

Implement transform(s) that returns a dict with three keys:

• upper — input uppercased
• lower — input lowercased
• clean — input stripped, lowercased, spaces replaced by _

[END TRANSMISSION]

Your Task

In starter/starter.py, build the dict using the four methods.

Objectives

• transform(" Hello World ")["clean"] returns "hello_world"
• All three keys present and correct for any string