from decimal import Decimal

# Parse API response
price = Decimal(order["price"])     # Decimal("0.65")
qty = Decimal(order["quantity"])    # Decimal("10")
notional = price * qty              # Decimal("6.50") — exact

# Send in requests
payload = {
    "quantity": str(qty),           # "10"
    "price": str(price),            # "0.65"
}

// Use string arithmetic libraries like bignumber.js or decimal.js
import Decimal from "decimal.js";

const price = new Decimal(order.price);     // "0.65"
const qty = new Decimal(order.quantity);     // "10"
const notional = price.times(qty);           // "6.50"

// Send in requests
const payload = {
  quantity: qty.toString(),
  price: price.toString(),
};

import "github.com/shopspring/decimal"

price, _ := decimal.NewFromString(order.Price)
qty, _ := decimal.NewFromString(order.Quantity)
notional := price.Mul(qty)  // "6.50"