drf - remove miliseconds from serializers.DateTimeField when sending response

Question

I have to write a serializer that returns datetime in the following formats:

2012-01-01T13:00:00+00:00 (utc_with_timezone)
2020-01-01T09:00:00 (must be in localtime without timezone info)

class SomeResponse(serializers.Serializer):
    modified = serializers.DateTimeField()  # AutoLastModifiedField(_('modified'))
    local_time = serializers.DateTimeField()

but the response for modified field contains miliseconds: 2022-01-01T18:14:05.378897+05:00
the response for local_time field contains timezone info and I have to convert it to local time

How can I manipulate the output format without changing the settings for the whole project?

Answer 1

I solved the problem by overriding to_representation of serializers.DateTimeField:

class SomeResponse(serializers.Serializer):
    modified = TimeZoneWithUTCField()  
    local_time = TimeZoneWithUTCField()


class TimeZoneWithUTCField(serializers.DateTimeField):
    def to_representation(self, value):
        if not value:
            return None

        value = value.strftime("%Y-%m-%dT%H:%M:%S%z")
        if value.endswith('+0000'):
            value = value[:-5] + '+00:00'
        return value