# Issue

I have a Django Rest Framework serializer with a DecimalField

```
serializers.DecimalField(max_digits=9, decimal_places=6)
```

Now if I try to deserialize data that contains a decimal with a higher precision (i.e. 50.1234567) the serializer raises a ValidationError:

```
"Ensure that there are no more than 6 decimal places."
```

This even happens if the last digit is 0. Is it possible to make the serializer round the given value to the maximum precision (i.e. 50.1234567 to 50.123457)? And if so how?

# Solution

After coercing the input to a Decimal the DecimalField validates the precision of the value in the aptly named, but undocumented, `validate_precision`

method. So to disable this validation one can override this method and simply return the input value:

```
class RoundingDecimalField(serializers.DecimalField):
def validate_precision(self, value):
return value
```

It turns out that doing this is enough to get the desired rounding behaviour.

After calling `validate_precision`

the DecimalField calls `quantize`

which will "Quantize the decimal value to the configured precision" (from the docstring).

The rounding mode for this quantisation process is controlled by the current active decimal context.

If a specific rounding mode is desired one can use the (again undocumented) `drf_braces.fields.custom.RoundedDecimalField`

field from django-rest-framework-braces. This field takes an optional rounding argument where one can specify the desired rounding mode.

Answered By - jaap3 Answer Checked By - Pedro (PHPFixing Volunteer)

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