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Matthew Smith
3,083 PointsWhy would I use partial, and not list comprehension?
In the challenge, I was asked to use partial and map to produce the discounted lists. While I understood how to use partial to solve the problem, I don't understand why I would use it.
Is this just a bad example of where partial produces better code, or is it more of a preference?
I would be keen to see an example where partial is a better alternative to list comprehension.
from functools import partial
prices = [
10.50,
9.99,
0.25,
1.50,
8.79,
101.25,
8.00
]
def discount(price, amount):
return price - price * (amount/100)
discount_10 = partial(discount, amount = 10)
discount_25 = partial(discount, amount = 25)
discount_50 = partial(discount, amount = 50)
prices_10 = map(discount_10, prices)
prices_25 = map(discount_25, prices)
prices_50 = map(discount_50, prices)
list_prices_10 = [ discount(price, 10) for price in prices]
Chris Freeman
Treehouse Moderator 68,423 PointsUnfortunately there isn’t. It’s been a long outstanding request to allow a revealing tag that would meet this need. Years ago embedded JavaScript was allow to hide code within posts, but was disallowed quickly.
You could put the spoiler code in a comment so that it’s less obvious as a poor substitute.
1 Answer
Chris Freeman
Treehouse Moderator 68,423 PointsThe primary lesson is to understand how partials work, so a simple example was chosen.
In a practical example, the base function may have a dozen parameters, of which, the local usage only needs to vary one of them. To repeatedly type the remaining “constant” parameters would be tedious and make the code harder to read. The reader would have to verify to be sure only the desired one was changing.
Sometime readability is sufficient enough reason. Otherwise the above code could have been written as:
lp_10, lp_25, lp_50 = [
[price - price * (amount/100)
for price in prices]
for amount in (10, 25, 50)]
Post back if you need more help. Good luck!!!
Matthew Smith
3,083 PointsMatthew Smith
3,083 Pointsas a sidenote for the moderators, is there a better way of me posing a question, and labelling it as a "spoiler" for folks looking for hints, but not the solution?