solution.py

# A bookseller has lots of books classified in 26 categories labeled A, B, ... Z.
# Each book has a code c of 3, 4, 5 or more capitals letters.
# The 1st letter of a code is the capital letter of 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 one of the stocklists 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 (in Haskell/Clojure/Racket a list of pairs):

# (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 "" (Clojure and Racket should return an empty array/list instead).


def stock_list(b, c):
    if not b:
        return ''
    return " - ".join(f"({x} : {sum(int(item.split()[1]) for item in b if item[0] == x)})" for x in c)