Net Profit per Trading Card

Problem

A collector resells trading cards. Every transaction is logged in one DataFrame.

`card_trades` (`card_trades.csv`): `card_name`, `action`, `trade_day`, `amount`. `action` is either `'purchase'` (money spent acquiring a card) or `'resale'` (money received selling it). `amount` is the money for that single transaction, and `(card_name, trade_day)` is unique. A card may be bought and sold many times.

The **net profit** of a card is the total received from resales minus the total spent on purchases, summed over all its transactions. A negative value means an overall loss.

Return a DataFrame with `card_name` and `net_profit` for each card. Rows may be in any order.

Input data

Example rows — the live problem includes the full dataset.

Expected output

Your answer should return 3 rows with the columns card_name, net_profit.

Starter code (Pandas (Python))

import pandas as pd

def net_profit_per_card(card_trades: pd.DataFrame) -> pd.DataFrame:
    # Your code here
    return card_trades

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