Task 1: Create and Inspect

Create:

readings = {"S1": 4.92, "S2": 5.31, "S3": 4.97}

Print:

• the S1 reading;
• the number of registered sensors;
• whether S4 is registered;
• a list of all sensor IDs.

Record predictions before running.

Task 2: Add, Update, and Remove

Perform these operations in order:

1. Add S4 with reading 5.02.
2. Correct S2 to 5.08.
3. Remove S3 with pop and store its old reading.
4. Attempt to remove S9 safely with a default.

Print the dictionary after each operation and print both returned values.

Check-Off A: Registry Semantics

Show your partner, then the instructor if requested:

• one assignment that adds a key;
• one assignment that replaces a value;
• one membership test;
• one safe lookup using get;
• one sentence explaining what dictionary membership tests.

Task 3: Summarize Readings

Complete:

def average_reading(readings):
    """Return the average of a non-empty reading dictionary."""
    total = 0
    for value in readings.values():
        total += value
    return total / len(readings)

Test with {“A”: 1.0, “B”: 2.0, “C”: 3.0}. The expected result is 2.0.

Task 4: Classify Every Sensor

Implement:

def voltage_status(value, low=4.75, high=5.25):
    """Return low, normal, or high."""
    ...

Then iterate over readings.items() and build:

statuses = {"S1": "normal"}  # continue for every sensor

Do not request input inside either function.

Task 5: Count the Statuses

Build a second dictionary mapping status names to counts.

status_counts = {}
for status in statuses.values():
    status_counts[status] = status_counts.get(status, 0) + 1

Print the result and verify that the sum of its values equals the number of sensors.

Task 6: Create the Sets

registered = set(readings)
active = {"S1", "S2", "S4", "S5"}
calibrated = {"S1", "S4"}
faulty = {"S2", "S5"}

Explain why set(readings) contains sensor IDs rather than reading values.

Confirm that empty braces create a dictionary and set() creates an empty set.

Task 7: Answer Relationship Questions

Write one set expression for each:

1. registered and active;
2. active but not calibrated;
3. registered sensors marked faulty;
4. every ID appearing in registered or active;
5. IDs appearing in exactly one of registered and active.

Print each result with a clear label.

Check-Off B: Set Reasoning

Draw or explain the result of one instructor-selected expression:

• registered & active
• active - calibrated
• registered & faulty
• registered | active
• registered ^ active

State what the result means in words before running it.

Task 8: Build a Fleet Report

Implement:

def fleet_report(readings, calibrated):
    """Return a dictionary containing summary information."""
    ...

Return a dictionary containing:

• sensor_count;
• average_reading;
• status_counts;
• needs_calibration.

Use your earlier functions instead of repeating their logic.

Optional Extension: Events from a File

The starter folder includes sensor_events.txt.

with open("sensor_events.txt", encoding="utf-8") as file:
    events = file.read().split()

event_counts = {}
for event in events:
    event_counts[event] = event_counts.get(event, 0) + 1

Move the Python file and text file together before running this extension.

Final Workflow

Your completed program should:

1. maintain one sensor-reading dictionary;
2. retrieve optional values without crashing;
3. build a sensor-status dictionary;
4. build status counts with get;
5. compare sensor groups with sets;
6. return one integrated report dictionary;
7. pass all supplied assertions.

Individual Checkoff

Each student completes one randomly selected action without partner help:

• safely look up a missing sensor;
• add versus update an entry and explain the difference;
• write one items() loop;
• repair a frequency-count statement;
• calculate and interpret one set relationship;
• explain why empty braces do not create an empty set.

See checkoff_rubric.qmd for the criteria.

Exit Ticket

Submit three short responses:

1. A safe lookup for S9 with default 0.0.
2. One loop that receives both sensor ID and reading.
3. The set expression for active sensors that need calibration.