Inventory management in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the class representing an inventory item.

LLD

class InventoryItem:
    def __init__(self, [1], quantity):
        self.[1] = [1]
        self.quantity = quantity

Drag options to blanks, or click blank then click option'

Astock

Blocation

Citem_id

Dprice

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'stock' instead of an identifier

Using 'price' which is not an identifier

Using 'location' which is unrelated here

The constructor needs an identifier for the inventory item, commonly called item_id.

2fill in blank

medium

Complete the code to add stock to the inventory item.

LLD

def add_stock(self, [1]):
    self.quantity += [1]

Drag options to blanks, or click blank then click option'

Aamount

Bitem

Cstock

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'item' which is confusing

Using 'stock' which is ambiguous

Using 'count' which is less clear

The method parameter should represent the amount of stock to add, commonly named amount.

3fill in blank

hard

Fix the error in the method to remove stock safely.

LLD

def remove_stock(self, amount):
    if self.quantity [1] amount:
        self.quantity -= amount
    else:
        raise ValueError('Not enough stock')

Drag options to blanks, or click blank then click option'

A>

B>=

C<

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' which allows removing more than available

Using '<=' which disallows removing all stock

Using '>' which disallows removing equal amount

We must check if current quantity is greater than or equal to the amount to remove.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps item IDs to quantities for items with quantity greater than 0.

LLD

stock_map = {item.[1]: item.[2] for item in inventory if item.quantity > 0}

Drag options to blanks, or click blank then click option'

Aitem_id

Bquantity

Cprice

Dlocation

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'price' or 'location' which are unrelated

Swapping keys and values

The dictionary keys should be item IDs and values should be quantities.

5fill in blank

hard

Fill all three blanks to create a method that returns a list of item IDs with quantity below a threshold.

LLD

def low_stock_items(self, [1]):
    return [item.[2] for item in self.inventory if item.quantity [3] [1]]

Drag options to blanks, or click blank then click option'

Athreshold

Bitem_id

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' in the condition

Returning quantities instead of item IDs

Using wrong parameter name

The method takes a threshold and returns item IDs where quantity is less than the threshold.

Practice

1. What is the primary purpose of an inventory management system?

easy

A. To track product quantities and prevent stock issues

B. To design product packaging

C. To manage employee schedules

D. To create marketing campaigns

Solution

1. Step 1: Understand inventory management goals

   Inventory management focuses on tracking product quantities to avoid running out or overstocking.

2. Step 2: Eliminate unrelated options

   Options about packaging, schedules, and marketing do not relate to inventory tracking.

3. Final Answer:

   To track product quantities and prevent stock issues -> Option A

4. Quick Check:

   Inventory management = tracking stock [OK]

Hint: Inventory systems track stock levels, not unrelated tasks [OK]

Common Mistakes:

• Confusing inventory with marketing or HR tasks
• Thinking inventory manages packaging design
• Assuming inventory handles employee schedules

2. Which of the following is the correct way to check if an item exists in an inventory dictionary named stock in Python?

easy

A. if stock.has_key('item'):

B. if 'item' in stock:

C. if stock.contains('item'):

D. if stock.exists('item'):

Solution

1. Step 1: Recall Python dictionary syntax

   To check if a key exists in a dictionary, use the in keyword.

2. Step 2: Identify correct syntax

   stock.has_key() is deprecated, and contains or exists are invalid methods.

3. Final Answer:

   if 'item' in stock: -> Option B

4. Quick Check:

   Use 'in' to check keys in dict [OK]

Hint: Use 'in' keyword to check keys in Python dicts [OK]

Common Mistakes:

• Using deprecated has_key() method
• Using non-existent methods like contains()
• Confusing method names for key checks

3. Given the Python code below, what will be the output?

stock = {'apple': 10, 'banana': 5}
stock['apple'] -= 3
print(stock['apple'])

medium

A. Error

B. 13

C. -3

D. 7

Solution

1. Step 1: Understand the initial stock

   Initially, 'apple' has quantity 10.

2. Step 2: Apply the subtraction operation

   Subtracting 3 from 10 results in 7.

3. Final Answer:

   7 -> Option D

4. Quick Check:

   10 - 3 = 7 [OK]

Hint: Subtract quantity correctly to find updated stock [OK]

Common Mistakes:

• Adding instead of subtracting
• Confusing keys or values
• Expecting an error due to subtraction

4. Identify the error in the following inventory update code snippet:

stock = {'apple': 5}
stock['banana'] -= 2
print(stock)

medium

A. No error, banana quantity becomes -2

B. SyntaxError due to invalid subtraction

C. KeyError because 'banana' does not exist in stock

D. TypeError because stock is not a list

Solution

1. Step 1: Check if 'banana' key exists

   'banana' is not in the stock dictionary initially.

2. Step 2: Understand dictionary behavior on missing keys

   Subtracting from a missing key causes a KeyError in Python.

3. Final Answer:

   KeyError because 'banana' does not exist in stock -> Option C

4. Quick Check:

   Missing key access = KeyError [OK]

Hint: Accessing missing dict keys causes KeyError [OK]

Common Mistakes:

• Assuming missing keys default to zero
• Expecting negative values without initialization
• Confusing error types

5. You are designing an inventory system that must handle multiple warehouses. Which design approach best ensures accurate stock counts across warehouses and prevents overselling?

hard

A. Maintain separate stock counts per warehouse and use transactions to update atomically

B. Keep a single global stock count without warehouse details

C. Update stock counts asynchronously without locking

D. Allow negative stock counts to handle overselling

Solution

1. Step 1: Consider multi-warehouse stock tracking

   Each warehouse should have its own stock count to track inventory accurately.

2. Step 2: Ensure atomic updates to prevent overselling

   Using transactions or locks ensures stock updates are consistent and prevent race conditions.

3. Final Answer:

   Maintain separate stock counts per warehouse and use transactions to update atomically -> Option A

4. Quick Check:

   Atomic updates + per-warehouse stock = accurate inventory [OK]

Hint: Use atomic transactions and per-warehouse counts [OK]

Common Mistakes:

• Using global stock ignores warehouse differences
• Updating asynchronously causes race conditions
• Allowing negative stock hides overselling problems