CurrencySerializerField for serializing CurrencyField in Django Rest Framework

currency_serializerfield.py

class CurrencySerializerField(DecimalField):
    """Serialize CurrencyField with 2 decimal places for presentation, keep 4 decimals for internal.

    This is implemented by BaseSerializer.

    Cannot just set `decimal_places=2` since it will error on input validation when 4 decimals.
    For rounding we use "bankers rounding", this is the most common practise but local law can differ.
    """
    def __init__(self, *args, max_digits=None, decimal_places=None, **kwargs):
        """Some values are hard coded as they are supposed to be the same for all.
        """
        super().__init__(*args, max_digits=10, decimal_places=4, **kwargs)
        self.rounding = decimal.ROUND_HALF_EVEN  # Bankers rounding

    def quantize(self, value: decimal.Decimal):
        """If the value is already quantized to 2 decimals, then leave it be.
        This allows to_representation() not to be overruled.
        """
        if value.as_tuple().exponent == -2:
            return value
        return super().quantize(value)

    def to_representation(self, value: decimal.Decimal):
        """Displaying results should only show 2 decimals.
        The super() calls quantize() where a little trick is applied to preserve 2 decimals.
        """
        if not isinstance(value, decimal.Decimal):
            value = decimal.Decimal(str(value).strip())

        value = value.quantize(
            decimal.Decimal('0.00'),  # 2 decimals
            rounding=self.rounding,
        )
        return super().to_representation(value)

Featured in this blog article: https://deepintodjango.com/keeping-accurate-amounts-in-django-with-currencyfield