I'm attempting a few simple calculations in a def clean method following validation (basically spitting out a euro conversion of retrieved uk product price on the fly). I keep getting a TypeError.

Full error reads:

Cannot convert {'product': , 'invoice': , 'order_discount': Decimal("0.00"), 'order_price': {...}, 'order_adjust': None, 'order_value': None, 'DELETE': False, 'id': 92, 'quantity': 8} to Decimal

so I guess django is passing through the entire cleaned_data form to Decimal method. Not sure where I'm going wrong - the code I'm working with is:

def clean_order_price(self):
    cleaned_data = self.cleaned_data
    data = self.data
    order_price = cleaned_data.get("order_price")
    if not order_price:
        try:
            existing_price = ProductCostPrice.objects.get(supplier=data['supplier'], product_id=cleaned_data['product'], is_latest=True)
        except ProductCostPrice.DoesNotExist:
            existing_price = None
        if not existing_price:
            raise forms.ValidationError('No match found, please enter new price')
        else:
            if data['invoice_type'] == 1:
                return existing_price.cost_price_gross
            elif data['invoice_type'] == 2:  
                exchange = EuroExchangeRate.objects.latest('exchange_date')
                calc = exchange.exchange_rate * float(existing_price.cost_price_gross)
                calc = Decimal(str(calc))
                return calc

    return cleaned_data

If the invoice is of type 2 (a euro invoice) then the system should grab the latest exchange rate and apply that to the matching UK pound price pulled through to get euro result.

Should performing a decimal conversion be a problem within def clean method?

Thanks