# Order Placement

This example demonstrates the complete workflow for placing an order on the 21X platform. It involves initializing the REST client to discover trading pairs, retrieving the `OrderBook` address for a specific pair, setting up the `OrderBook` class, and submitting an order.

***

## Steps to Place an Order

### Initialize the REST API Client

Use the REST client to fetch trading pairs and locate the target trading pair.

```python
from x21_sdk import Client

# Initialize the REST client
client = Client()
```

### Fetch Trading Pairs

Retrieve a list of available trading pairs and identify the pair of interest.

```python
trading_pairs = get_trading_pairs.sync(client=client)

for pair in trading_pairs.items:
    print(pair)

# Select a trading pair
selected_pair = next(
    pair for pair in trading_pairs if pair.base_token_data.symbol == 'DEVAMDIII'
)

orderbook_address = selected_pair.smart_contract_order_book
print(f'OrderBook Contract Address: {orderbook_address}')
```

### Retrieve Price Information

Use the `getTradeInfo` endpoint to retrieve trade information for the selected trading pair.

```python
from x21_sdk.client.api.public_market_data import get_trade_info
from x21_sdk.client.models import TradingStatusEnum

trade_info = get_trade_info.sync(
    client=client,
    id=selected_pair.id,
)

assert trade_info.trading_status == TradingStatusEnum.CONTINUOUS_TRADING
print(f'current price: {trade_info.last_price}')
```

### Initialize the `OrderBook` Class

Use the retrieved `orderbook_address` to interact with the smart contract.

```python
from x21_sdk import OrderBook

# Initialize the OrderBook with Web3 provider and contract address
order_book = OrderBook(
  private_key='your_private_key',
  orderbook_addr=orderbook_address,
  rpc_url='https://polygon-mainnet.g.alchemy.com/v2/YOUR_API_KEY',
)
```

### Set Token Allowances

Before placing an order, ensure that the allowances for the base and quote tokens are set appropriately.

```python
from decimal import Decimal

order_book.set_base_allowance(amount=Decimal('1005'))
order_book.set_quote_allowance(amount=Decimal('10'))
```

### Place an Order

Use the `create_buy_order` or `create_sell_order` methods to submit your order.

```python
# Example: Place a buy order
order_book.create_buy_order(
    quantity=Decimal('10'),
    price=Decimal('99.75'),
    allowance=False,
)

print('Buy order placed successfully!')

# Example: Place a sell order
order_book.create_sell_order(
    quantity=Decimal('10'),
    price=Decimal('100.25'),
    allowance=False,
)

print('Sell order placed successfully!')
```

***

#### Summary of Workflow

1. Use the REST API client to fetch trading pairs and locate the `OrderBook` address.
2. Initialize the `OrderBook` class with the retrieved address.
3. Ensure sufficient token allowances are set for the transaction.
4. Submit a buy or sell order using the `OrderBook` class.