How to name serializer field different than its class variable

[jacobg]

Suppose I want to serialize an object that contains a field named 'in'.

The naive approach would be something like this:

from rest_framework import serializers

class MySerializer(serializers.Serializer):
   in = serializers.DateTimeField()

However, in is a Python keyword, and will raise an error: SyntaxError: invalid syntax

Is there a simple solution to make MySerializer serialize that field using the name 'in with a different class variable name?

In DRF version 3.9.4, I made the following solution:

class TargetFieldMixin(serializers.Field):
    def __init__(self, *args, **kwargs):
        self.target = kwargs.pop('target', None)
        super(TargetFieldMixin, self).__init__(*args, **kwargs)

class TargetSerializerMixin(serializers.Serializer):
    @property
    def fields(self):
        fields = super(TargetSerializerMixin, self).fields

        if not hasattr(self, '_field_targets_updated'):
            for field_name, field in list(fields.items()):
                target = getattr(field, 'target', None)
                if target and field_name != target:
                    # mutation takes place on superclass's internal fields dictionary
                    fields.pop(field_name)
                    fields[target] = field
                    field.field_name = target
            setattr(self, '_field_targets_updated', True)

        return fields

class MySerializer(TargetSerializerMixin):
   in_ = type('Field', (serializers.DateTimeField, TargetFieldMixin), {})(target='in')

It worked great on that version, but upon updating to DRF version 3.13.1, it broke. I was able to fix it by changing the TargetSerializerMixin implementation to the following:

class TargetSerializerMixin(serializers.Serializer):
    @property
    def fields(self):
        if not hasattr(self, '_field_targets_updated'):
            fields = self._declared_fields
            for field_name, field in list(fields.items()):
                target = getattr(field, 'target', None)
                if target and field_name != target:
                    fields.pop(field_name)
                    fields[target] = field
                    field.field_name = target
            setattr(self, '_field_targets_updated', True)

        return super().fields

Although it does work, it's fragile, as it relies on internal implementation details. As it already broke once, it could break again in a future DRF update. Is there a safer solution?

Thanks!

[jerinpetergeorge]

I'm not sure, but, are you trying to achieve something like this? 🤔 @jacobg

In [12]: from rest_framework import serializers
    ...: 
    ...: 
    ...: class SimpleSerializer(serializers.Serializer):
    ...:     _in = serializers.CharField(source="in")
    ...: 

In [13]: s = SimpleSerializer(data={"_in": "this is my data"})

In [14]: s.is_valid(True)
Out[14]: True

In [15]: dict(s.validated_data)
Out[15]: {'in': 'this is my data'}

s.validated_data is returning data with in as field