Build the inventory again, with proper errors and a stock report.
What to build
A class with a custom exception and two kinds of report.
Requirements
add ITEM Kadds stock. It prints nothing.remove ITEM Kprintsremoved, orout of stock: need X moreusing a customOutOfStockexception.reportprints each item with stock asITEM K, in alphabetical order, orempty.low Mprints the names of items with fewer thanMleft, alphabetically on one line, ornone.
Input
The first line has n. Each of the next n lines is a command.
Output
Only what the commands above print.
Constraints
n is from 1 to 1000. All numbers are from 1 to 1000000. Items at zero remain known, but they are not in the report.
Example
Input:
5
add pen 10
add ink 2
remove pen 3
report
low 5
Output:
removed
ink 2
pen 7
ink
Why it works
Raising a specific error lets the method report a problem without printing anything, so the class stays reusable and the main loop decides what to show.
Examples
Example 1 · Input
5 add pen 10 add ink 2 remove pen 3 report low 5
Expected output
removed ink 2 pen 7 ink
Example 2 · Input
2 remove pen 1 report
Expected output
out of stock: need 1 more empty
Prompts inside input() are ignored when checking, so input("n: ") is fine.
Hints
Hint 1
Define OutOfStock so that it inherits from Exception.
Hint 2
remove raises it with the shortfall, and the main loop catches it.
Hint 3
report sorts the items and skips those with zero left.
Solution
Show one correct solution (try it yourself first)
class OutOfStock(Exception):
pass
class Inventory:
def __init__(self):
self.stock = {}
def add(self, item, amount):
self.stock[item] = self.stock.get(item, 0) + amount
def remove(self, item, amount):
have = self.stock.get(item, 0)
if have < amount:
raise OutOfStock(amount - have)
self.stock[item] = have - amount
def report(self):
return [f"{item} {k}" for item, k in sorted(self.stock.items()) if k > 0]
def low(self, minimum):
return sorted(item for item, k in self.stock.items() if k < minimum)
shop = Inventory()
n = int(input())
for _ in range(n):
parts = input().split()
if parts[0] == "add":
shop.add(parts[1], int(parts[2]))
elif parts[0] == "remove":
try:
shop.remove(parts[1], int(parts[2]))
print("removed")
except OutOfStock as error:
print(f"out of stock: need {error} more")
elif parts[0] == "report":
lines = shop.report()
print("\n".join(lines) if lines else "empty")
else:
names = shop.low(int(parts[1]))
print(" ".join(names) if names else "none")