The DECIMAL type field fetch data become string

Question

In my table:

My discount type is DECIMAL:

My data in table:

But why when I fetch data in API, there gets string?

I use Django and Django REST framework as the backend.

belong_product: "server"
ctime: "2018-04-11T15:41:15.744959+08:00"
desc: ""
discount: "0.005"
id: 1
is_enable: false
max_count: 5
min_count: 0
name: "one"
uptime: "2018-04-11T15:41:15.745226+08:00"

My ListAPI view:

class DiscountItemByUserOwnCountListAPIView(ListAPIView):
    serializer_class = DiscountItemByUserOwnCountSerializer
    permission_classes = [IsSuperAdmin]
    pagination_class = CommonPagination
    def get_queryset(self):
        return DiscountItemByUserOwnCount.objects.all()

My model:

class DiscountItemByUserOwnCount(models.Model):
    name = models.CharField(max_length=16, help_text="name")
    desc = models.CharField(max_length=512, null=True, blank=True, help_text="desc")
    min_count = models.IntegerField(help_text="min")
    max_count = models.IntegerField(help_text="max")   
    discount = models.DecimalField(max_digits=4, decimal_places=3, default=0.000, unique=True,
                                   help_text="point")  
    belong_product = models.CharField(max_length=16, help_text="belongDISCOUNT_PRODUCT_TYPE")

    is_enable = models.BooleanField(default=False)

    ctime = models.DateTimeField(auto_now_add=True)
    uptime = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.name
    def __unicode__(self):
        return self.name

    class Meta:
        ordering = ['min_count', '-id']

`COERCE_DECIMAL_TO_STRING:False` is not working then you might check your `views.py` while `returing` the `Response` it should be like `return Response(serializer.data)` instead of `return Response(f'{serializer.data}')` — Azhar Uddin Sheikh, Aug 16 '23 at 08:32

score 34 · Accepted Answer · edited Feb 08 '22 at 12:25

34

The default decimal representation in Django REST framework is string. To disable this behavior, add following to your settings.py file:

REST_FRAMEWORK = {
    'COERCE_DECIMAL_TO_STRING': False,
    # Your other settings
    ...
}

See details in the documentation.

edited Feb 08 '22 at 12:25

Peter Mortensen

30,738
21
105
131

answered Apr 11 '18 at 09:00

neverwalkaloner

46,181
7
92
100

but why it default is to string in DRF? what's the benefit? – user7693832 Apr 11 '18 at 09:03
1

@244boy to make value localization more convenient. Based on localization settings backend will return foramtted string "10.05" or "10,05" for example. – neverwalkaloner Apr 11 '18 at 09:06

score 4 · Answer 2 · answered Apr 11 '18 at 09:13

4

It is a string because otherwise you'll get rounding errors. This can be easily seen using a Python shell:

>>> import decimal
>>> from decimal import Decimal
>>> Decimal(0.3)
Decimal('0.299999999999999988897769753748434595763683319091796875')
>>> Decimal('0.3')
Decimal('0.3')
>>>

Also note that JSON doesn't have decimal. Only integers and floats.

answered Apr 11 '18 at 09:13

Linovia

19,812
4
47
48

and the `0.30` in decimal will be convert to `0.3` if I request from API if the `COERCE_DECIMAL_TO_STRING : True`, alright? – user7693832 Apr 11 '18 at 09:23
2

COERCE_DECIMAL_TO_STRING is True by default. If you turn it to False, you'll have float instead of string and will loose the decimal precision, beware to that. – Linovia Apr 11 '18 at 09:29

fire_demesne · Answer 3 · 2022-12-13T00:58:54.940

4

The default behaviour of the Decimal field is string in REST_FRAMEWORK to override for the whole app we can use

REST_FRAMEWORK = {
    'COERCE_DECIMAL_TO_STRING': False,
    # Your other settings
    ...
}

but if You want to override it for one field You can do as following

field = serializers.DecimalField(coerce_to_string=False)

by default coerce_to_string is True. checkout this out

edited Dec 13 '22 at 00:58

answered Dec 13 '22 at 00:57

fire_demesne

79
5

The DECIMAL type field fetch data become string

3 Answers3

Linked

Related