Handling money with Python and py-moneyed

py-moneyed.ipynb

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   "source": [
    "This is just a spike on handling money with Python and [py-moneyed](https://github.com/limist/py-moneyed).\n",
    "\n",
    "Just a setup, I created a test table in PostgreSQL with:\n",
    "```sql\n",
    "CREATE TABLE py_moneyed_test (\n",
    "    id serial PRIMARY key,\n",
    "    price_amount NUMERIC,\n",
    "    price_currency char(3)\n",
    ")\n",
    "```"
   ]
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  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
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   "source": [
    "from moneyed import Money as BaseMoney\n",
    "\n",
    "\n",
    "class Money(BaseMoney):\n",
    "    # This is needed to be able to use sqlalchemy composite values\n",
    "    # We have to use this class instead of moneyed.Money in the codebase\n",
    "    def __composite_values__(self):\n",
    "        return self.amount, self.currency.code"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
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   "source": [
    "from sqlalchemy import create_engine, Column, Numeric, String, Integer\n",
    "from sqlalchemy.orm import composite, sessionmaker\n",
    "from sqlalchemy.ext.declarative import declarative_base\n",
    "\n",
    "engine = create_engine('postgresql://postgres:password@localhost/money_test')\n",
    "Session = sessionmaker(bind=engine)\n",
    "session = Session()\n",
    "\n",
    "Base = declarative_base()\n",
    "\n",
    "\n",
    "class PricedItem(Base):\n",
    "    __tablename__ = 'py_moneyed_test'\n",
    "\n",
    "    id = Column(Integer, primary_key=True)\n",
    "    price_amount = Column(Numeric)\n",
    "    price_currency = Column(String(3))\n",
    "\n",
    "    price = composite(Money, price_amount, price_currency)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "some_price = Money(59.50, 'USD')\n",
    "item = PricedItem()\n",
    "item.price = some_price\n",
    "session.add(item)\n",
    "session.commit()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<Money: 59.5 USD>"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "fetched_obj = session.query(PricedItem).all()[-1]\n",
    "fetched_obj.price"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "fetched_obj.price == some_price"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<Money: 80.49 USD>"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "some_price + Money('20.99', 'USD')"
   ]
  }
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