[Solved] You have this code snippet to add a transaction record:def add_transaction(history, transaction): if transaction['id'] not in [t['id'] for t in history]: history.append(transaction) else:... | LLD

LLD - Design — Splitwise (Expense Sharing)

You have this code snippet to add a transaction record:

def add_transaction(history, transaction):
    if transaction['id'] not in [t['id'] for t in history]:
        history.append(transaction)
    else:
        print("Duplicate transaction")

history = [{"id": "t1"}]
add_transaction(history, {"id": "t1"})

What is the output when running this code?

ADuplicate transaction

BKeyError exception

CNo output, transaction added

DTypeError exception

Step-by-Step Solution

Solution:

Step 1: Check if transaction ID exists in history
The code checks if 't1' is already in the list of IDs in history.
Step 2: Since 't1' exists, print duplicate message
The else branch runs and prints "Duplicate transaction".
Final Answer:
Duplicate transaction -> Option A
Quick Check:
Duplicate ID detected = print message [OK]

Quick Trick: Check for existing ID before adding to avoid duplicates [OK]

Common Mistakes:

MISTAKES

Assuming transaction is added anyway
Expecting an exception instead of print
Confusing list comprehension syntax

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You have this code snippet to add a transaction record:

Step 1: Check if transaction ID exists in history

Step 2: Since 't1' exists, print duplicate message

Final Answer:

Quick Check:

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