Build a Themed Collection

Mission: build-an-object-collection

Learning target: Represent exactly three related objects as dictionaries in one list, trace the first iteration of one plain for loop, and print a design inventory before transferring the values to package YAML.

M06 is complete only after you interact with all three objects.

A dictionary keeps the properties of one object together as key-value pairs.

{"name": "Sun Seed", "x": 180, "y": 180, "color": "gold"}

• The keys are "name", "x", "y", and "color".
• Each key has one value after its colon.
• One complete dictionary plans one world object.

objects = [
    {"name": "Sun Seed", "x": 180, "y": 180, "color": "gold"},
    {"name": "Rain Bell", "x": 380, "y": 300, "color": "blue"},
    {"name": "Wind Flower", "x": 620, "y": 420, "color": "pink"},
]

Keep exactly three dictionaries. Their list order is the breadcrumb order: Sun Seed → Rain Bell → Wind Flower.

object_record["x"]

The square brackets ask the current dictionary for the value stored under "x". For the Sun Seed record, the result is 180.

The spelling must match the key exactly. Python does not guess a missing or differently spelled property.

for object_record in objects:
    print(
        object_record["name"],
        object_record["x"],
        object_record["y"],
        object_record["color"],
    )

Python takes each dictionary from objects in order, gives it the temporary name object_record, and runs the same indented print.

Do not run the starter yet. Fill in this trace on paper:

object_record is the record named: __________
object_record["x"] is: __________
the first printed line will be: ______________________________

Then circle any duplicate name or coordinate and any missing property you predict will cause trouble.

objects = [
    {"name": "Sun Seed", "x": 180, "y": 180, "color": "gold"},
    {"name": "Rain Bell", "x": 380, "y": 300, "color": "blue"},
    {"name": "TODO: third garden object", "x": 620, "y": 420, "color": "green"},
]

1. Check your first-iteration trace.
2. Replace only the third record’s TODO name and choose its color.
3. Keep all four properties in every record.
4. Run python lessons/sessions/s06/student/starter.py.

A completed canonical example prints:

Sun Seed 180 180 gold
Rain Bell 380 300 blue
Wind Flower 620 420 pink

Point to one lookup in your loop and explain which dictionary supplies its value on the first iteration.

broken_record = {
    "name": "Wind Flower",
    "x": 520,
    "color": "pink",
}

print(broken_record["y"])

KeyError: 'y'

The lookup asks for "y", but the record has no such key. Add an integer y property before reading it, then rerun successfully.

Python never executes from the package. The validated YAML values are what the runtime loads into the visible world.

• Keep exactly three package objects.
• Give them distinct names, positions, colors, near responses, and interaction responses.
• Make Sun Seed lead toward Rain Bell, and Rain Bell lead toward Wind Flower.
• Let Wind Flower point toward a gate hidden in the sky.

explore-package validate lessons/sessions/s06/student/explorer-package

valid: starlight-garden 0.1.0

If validation fails, read its file and field location. Repair the YAML error separately from the Python KeyError exercise.

explore-package trail \
  examples/explorer-packages/nova-character \
  lessons/sessions/s06/student/explorer-package \
  --player "nova-character:nova" \
  --mission-id "build-an-object-collection" \
  --name "S06 Build a Themed Collection"

This mission uses the standard, plain Trail presentation. Nova and the three package objects are enough; there is no NPC or lantern dependency.

1. Move Nova near Sun Seed and press E.
2. Follow its breadcrumb to Rain Bell and press E.
3. Follow Rain Bell to Wind Flower and press E.
4. Confirm the mission state changes to Complete only after all three visits.

Today’s solution has a deliberately small shape:

• No list comprehension.
• No nested loop.
• No second loop.
• No fourth object.

Strengthen the three existing response strings if you finish early; do not add another mechanic.

• Dictionary: Which properties belong to one record?
• List: Why does the order of the three records matter?
• Loop: What changes from the first iteration to the second?
• Boundary: Which file plans values, and which files drive the Trail?
• Mission: Why is M06 incomplete after only two interactions?

That’s the next session on the class calendar. For now, keep the final breadcrumb’s skyward clue as story only.

Save your files. Be ready to trace the first iteration, explain one key lookup, and show that all three objects were required for completion.

What we learned in Python today →