feat(other): add grocery store cart model (v3)

[nickzerjeski]

Describe your change:

Fixes #14050

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[Copilot]

Pull request overview

Adds a small, console-free “grocery store cart” model to the other/ collection, intended to address issue #14050 by encapsulating cart state (quantities) and total calculation behind a class API.

Changes:

• Introduces GroceryStoreCart with add_item(), remove_item(), and total_price().
• Adds basic validation (empty catalog, unknown item, non-positive quantity) and doctest-based usage example.
• Adds a __main__ doctest runner.

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[Copilot]

remove_item() currently treats quantity values larger than the current quantity as “remove everything” (because remaining <= 0 pops the item). This makes it easy to silently remove more items than are present. Consider raising a ValueError when quantity > current (and only popping when quantity == current).

Suggested change

	if (remaining := current - quantity) > 0:
	self.quantities[item] = remaining
	else:
	self.quantities.pop(item, None)
	if quantity > current:
	raise ValueError("quantity exceeds amount present in the cart")
	if quantity == current:
	self.quantities.pop(item, None)
	else:
	self.quantities[item] = current - quantity

[Copilot]

This total_price() return line is likely over the repo’s configured line-length limit (ruff/pycodestyle E501). Please wrap the sum(...) call across multiple lines to avoid lint failures.

Suggested change

	self.price_catalog[item] * qty for item, qty in self.quantities.items()
	self.price_catalog[item] * qty
	for item, qty in self.quantities.items()

[Copilot]

The doctest only covers the happy path. Since __init__(), add_item(), and remove_item() introduce several error branches (empty catalog, unknown items, non-positive quantities), please add doctest cases that assert the expected exceptions/messages so these behaviors are exercised by CI.

Suggested change

	3.5
	3.5
	>>> GroceryStoreCart({})
	Traceback (most recent call last):
	...
	ValueError: price_catalog cannot be empty
	>>> cart.add_item("bread")
	Traceback (most recent call last):
	...
	KeyError: "'bread' is not in the catalog"
	>>> cart.add_item("apple", 0)
	Traceback (most recent call last):
	...
	ValueError: quantity must be positive
	>>> cart.remove_item("milk", 0)
	Traceback (most recent call last):
	...
	ValueError: quantity must be positive
	>>> empty_cart = GroceryStoreCart({"apple": 1.5})
	>>> empty_cart.remove_item("apple")
	Traceback (most recent call last):
	...
	KeyError: "'apple' is not present in the cart"