Exercise 2: One-to-Many Adapter

Goal

Extend Adapter from one object to one object into one object to many objects.

In Exercise 1, one LegacyReading became one adapted reading.

Now one LegacyBatch contains many raw readings. The client code wants to iterate over clean TemperatureReading objects.

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Story

The old greenhouse gateway sends readings in batches.

A batch contains:

device_id
[(timestamp, fahrenheit), (timestamp, fahrenheit), ...]

But the rest of your application wants this:

for reading in readings:
    process(reading.sensor_id, reading.timestamp, reading.celsius)

You do not want every caller to know how to unpack tuples, skip missing values, or convert Fahrenheit to Celsius.

So you will build an iterable adapter.

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Your task

Open exercise2.py and implement LegacyBatchToReadingsAdapter.

The adapter should:

1. accept a LegacyBatch,
2. create a collection of TemperatureReading objects,
3. skip readings where Fahrenheit is None,
4. convert Fahrenheit to Celsius,
5. round Celsius to two decimal places,
6. implement __iter__,
7. implement __len__.

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Expected behavior

batch = LegacyBatch(
    device="greenhouse-1",
    rows=[
        (100, 68.0),
        (101, 86.0),
        (102, None),
    ],
)

adapter = LegacyBatchToReadingsAdapter(batch)

assert len(adapter) == 2
assert list(adapter)[0].celsius == 20.0
assert list(adapter)[1].celsius == 30.0

The missing reading is skipped.

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Run the tests

python exercise2.py