Exercise 2: Deep Copying Nested State

Goal

Improve the dashboard prototype so cloned dashboards do not accidentally share nested mutable objects.

This is the most important practical detail in the Prototype pattern.

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Story

The first clone worked for top-level fields.

But dashboards contain nested mutable state:

widgets -> list of Widget objects
filters -> dictionary of filter values

If two dashboards share the same filters dictionary or the same Widget objects, changing one dashboard can accidentally change the other.

That is not a safe clone.

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Your task

Open exercise2.py and implement:

def clone(self, **changes) -> "Dashboard":
    ...

This time the clone must be independent from the original, including:

• the widgets list,
• each Widget inside the list,
• the filters dictionary.

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Tests to satisfy

The tests check that:

• the clone is a new Dashboard,
• changing clone filters does not affect the original,
• changing clone widgets does not affect the original,
• the nested objects are not the same objects in memory.

Run:

python exercise2.py

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Hint

Use copy.deepcopy().

The point of this exercise is to feel the difference between:

copy.copy(obj)

and:

copy.deepcopy(obj)