Python interview questions

Answer

Use a dictionary when the main operation is finding and updating a total by item code: each code maps to one current quantity, so an update is usually constant-time. A list of pairs is useful if event order or duplicate records must be retained, but repeatedly searching that list for a code takes linear time. Keep the input events separately if an audit trail is required; a summary dictionary should not pretend to be that audit trail.

Answer

It prints rice first because -8 sorts before -5, then flour before tea because the second key component compares codes alphabetically. The tie does not retain tea before flour: the key explicitly asks for alphabetical ordering, which overrides input order. Python's stable sort matters only when complete sort keys compare equal. This is a useful way to state a business tie-break without a second pass.

[('rice', 8), ('flour', 5), ('tea', 5)]

Answer

Required stock is daily demand multiplied by lead days. Subtract current stock and clamp at zero: an item with more than enough stock should not have a negative order quantity. The first item needs twelve units but has seven, so its shortfall is five; the second needs ten but has twenty, so it needs none. In production, validate non-negative inputs and decide how to handle demand forecasts that change over time.

def shortfall(current, daily, days):
    return max(0, daily * days - current)

print(shortfall(7, 3, 4))
print(shortfall(20, 2, 5))

5
0

Answer

Do not silently turn missing lead time into zero: that makes an urgent item appear fully stocked. Agree on a data-quality policy with the report owner. A useful default is to reject or quarantine the row, report its item code and reason, and still compute the valid rows; a critical procurement workflow may instead fail the whole report. Keep rejected-row counts visible, log enough detail for correction, and never mix unknown values with genuine zero-day delivery.

Answer

Accumulating N records in a dictionary is O(N) on average, assuming ordinary hash-table behaviour. Sorting K distinct item codes costs O(K log K), so the combined cost is O(N + K log K), with O(K) summary storage. Do not claim that dictionary iteration itself is an alphabetical report: even if insertion order is retained, that order describes input, not the desired ranking. The sort key should also specify how equal shortages are resolved.