# How to Solve: Help the Bookseller Challenge in Python

0
107

A bookseller has lots of books classified in 26 categories labeled A, B, &mldr; Z. Each book has a code c of 3, 4, 5 or more characters. The 1st character of a code is a capital letter which defines the book category.

In the bookseller’s stocklist each code c is followed by a space and by a positive integer n (int n >= 0) which indicates the quantity of books of this code in stock.

For example an extract of a stocklist could be:

`L = {"ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"}.`
or
`L = ["ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"] or ....`
You will be given a stocklist (e.g. : L) and a list of categories in capital letters e.g :

`M = {"A", "B", "C", "W"}`
or
`M = ["A", "B", "C", "W"] or ...`
and your task is to find all the books of L with codes belonging to each category of M and to sum their quantity according to each category.

For the lists L and M of example you have to return the string:

`(A : 20) - (B : 114) - (C : 50) - (W : 0)`
where A, B, C, W are the categories, 20 is the sum of the unique book of category A, 114 the sum corresponding to “BKWRK” and “BTSQZ”, 50 corresponding to “CDXEF” and 0 to category ‘W’ since there are no code beginning with W.

If `L` or `M` are empty return string is “”.

Notes:

• In the result codes and their values are in the same order as in M.
• See “Samples Tests” for the return.

## The Solution in Python#

### Option 1#

``````def stock_list(listOfArt, listOfCat):
if (len(listOfArt) == 0) or (len(listOfCat) == 0):
return ""
result = ""
for cat in listOfCat:
total = 0
for book in listOfArt:
if (book == cat):
total += int(book.split(" "))
if (len(result) != 0):
result += " - "
result += "(" + str(cat) + " : " + str(total) + ")"
return result
``````

### Option 2#

``````from collections import Counter

def stock_list(listOfArt, listOfCat):
if not listOfArt:
return ''
codePos = listOfArt.index(' ') + 1
cnt = Counter()
for s in listOfArt:
cnt[s] += int(s[codePos:])
return ' - '.join('({} : {})'.format(cat, cnt[cat]) for cat in listOfCat)
``````
``````def stock_list(stocklist, categories):
if not stocklist or not categories:
return ""
return " - ".join(
"({} : {})".format(
category,
sum(int(item.split()) for item in stocklist if item == category))
for category in categories)
``````

## Test cases to validate the solution#

``````from solution import stock_list
import codewars_test as test

@test.describe("Testing")
def _():
@test.it("Tests")
def _():
b = ["BBAR 150", "CDXE 515", "BKWR 250", "BTSQ 890", "DRTY 600"]
c = ["A", "B", "C", "D"]
test.assert_equals(stock_list(b, c), "(A : 0) - (B : 1290) - (C : 515) - (D : 600)")

b = ["ABAR 200", "CDXE 500", "BKWR 250", "BTSQ 890", "DRTY 600"]
c = ["A", "B"]
test.assert_equals(stock_list(b, c), "(A : 200) - (B : 1140)")

b = ["CBART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"]
c = ["A", "B", "C", "W"]
test.assert_equals(stock_list(b, c), "(A : 0) - (B : 114) - (C : 70) - (W : 0)")

b = ["ROXANNE 102", "RHODODE 123", "BKWRKAA 125", "BTSQZFG 239", "DRTYMKH 060"]
c = ["B", "R", "D", "X"]
test.assert_equals(stock_list(b, c), "(B : 364) - (R : 225) - (D : 60) - (X : 0)")

b = []
c = ["B", "R", "D", "X"]
test.assert_equals(stock_list(b, c), "")

b = ["ROXANNE 102", "RHODODE 123", "BKWRKAA 125", "BTSQZFG 239", "DRTYMKH 060"]
c = []
test.assert_equals(stock_list(b, c), "")

b = ["ROXANNE 102", "RHODODE 123", "BKWRKAA 125", "BTSQZFG 239", "DRTYMKH 060"]
c = ["U", "V", "R"]
test.assert_equals(stock_list(b, c), "(U : 0) - (V : 0) - (R : 225)")
``````