Two Dictionaries and a Sum!

[Chris Angelico]

On Sat, May 18, 2013 at 2:19 PM, Bradley Wright
<bradley.wright.biz at gmail.com> wrote:
> Confusing subject for a confusing problem (to a novice like me of course!)
> Thx for the help in advance folks
>
> I have (2) dictionaries:
>
> prices = {
>     "banana": 4,
>     "apple": 2,
>     "orange": 1.5,
>     "pear": 3
> }
>
> stock = {
>     "banana": 6,
>     "apple": 0,
>     "orange": 32,
>     "pear": 15
> }
>
> Here's my instructions:
>
> consider this as an inventory and calculate the sum (thats 4*6 = 24 bananas!)

Let me reword your problem a little, maybe it'll be a bit clearer.
You're trying to calculate the total value of all stock on hand, eg
for insurance purposes. That's not 24 bananas, that's $24 of bananas.
And the part you want now is to get the total value of your entire
stock. Great! You're very close to there...

> HERES MY CODE:
>
> for key in prices:
>     print prices[key]*stock[key]
>
> ISSUE:
> I need to find a way to add all of those together...any pointers?

... you just need to accumulate a sum. Since this is almost certainly
homework, I won't give you the answer, but here are a few pointers:

* You'll need a single variable (I use the term sloppily, Python
doesn't actually have variables per se) which will collect the final
total.
* Inside your loop, you're currently printing out an int/float with
the value of the current item. Just add it onto your accumulator.
* Python will happily work with integers and floats together, so you
can just do what's obvious and it'll work.

See where that takes you. Have fun! :)

ChrisA