seed: curriculum content

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

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+---
+type: challenge
+title: "The Methods"
+xp: 50
+duration: 30
+difficulty: 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:
+>
+> ```python
+> "  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