The solution provided here for the
Discounts
coding exercise includes two sources files, cart.py and
test_cart.py, and a Pipfile to be used with pipenv.
To run the tests:
$ pipenv install --dev
$ pipenv run pytest
I defined the data model using namedtuple subclasses. The cart application is
treated as an instance of cart.Application namedtuple with fields for the
product and discount databases. The cart.display_cart() function takes as an
instance of cart.Application (the global state) and an instance of
cart.Order. The only function that needs to know the global state is
display_cart whereas other functions are called with lists of cart.ItemPrice
built up from the line items in an order.
I liberally made use of list comprehensions here as a way to code in Python in a more functional style. I generally find them easier to read but they do present problems for debugging in Python and other programmers might not agree they are as readable as for loops.
The test cases reproduce the examples in the challenge description. I have added one more test case for the case where a product discount must be applied to multiple quantities of a product. I have assumed the cart display should include the total original sum of the quanitities for that item (e.g., $40 in this case rather than $20).