Django rest framework, AttributeError: 'str' object has no attribute 'data' and unable to upload image using forms

Question

I'm struggling with recruitment task, i'm pretty new in Django and I haven't used rest framework before. I'm trying to built view where user can upload picture and set how long link should be valid(in range 3000-30000, validation works for that). This feature works thru postman instaed of received link to file I have following error:

    return renderer.render(serializer.data, None, {'style': style})
AttributeError: 'str' object has no attribute 'data'

When I try to upload file using website serializer is not passing validation.

I'm using render_form in html file and result in QueryDict is different than in postman so i guess thats the issue, however no idea how to solve it: using website:

'image_url': ['airplane.jpg'],

using postman:

 'image_url': [<InMemoryUploadedFile: airplane.jpg (image/jpeg)>]

models.py:

import datetime

from django.db import models
from django.contrib.auth.models import User
from images.validators import expiring_in_validator


def upload_to(instance, filename):
    unique_identify = str(int(datetime.datetime.now().timestamp()))
    return f"media/{filename}-{unique_identify}"

# Create your models here.
class Image(models.Model):
    uploaded_by = models.ForeignKey(User, on_delete=models.CASCADE)
    image_url = models.ImageField(upload_to=upload_to)
    expiring_within = models.IntegerField(validators=[expiring_in_validator])

serializers.py:

from rest_framework import serializers
from images.models import Image


class PostSerializer(serializers.ModelSerializer):
    class Meta:
        model = Image
        fields = ['image_url', 'expiring_within']

views.py:

from django.shortcuts import render
from django.views import View
from rest_framework import status
from rest_framework.parsers import FormParser, MultiPartParser
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView
from rest_framework.renderers import TemplateHTMLRenderer

from images.serializers import PostSerializer


# Create your views here.
class AddImage(APIView):
    renderer_classes = [TemplateHTMLRenderer]
    # permission_classes = [IsAuthenticated]
    template_name = "add_image.html"
    parser_classes = [MultiPartParser, FormParser]
    def get(self, request):
        serializer = PostSerializer()
        return Response({"serializer": serializer})

    def post(self, request):
        serializer = PostSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save(uploaded_by=self.request.user)
            return Response(serializer.data, status=status.HTTP_200_OK)

html:

<form method="post">
{% csrf_token %}
        {% render_form serializer %}

    <input type="submit" value="Wyślij">
</form>

Forms works now but after uploading image instead of link I'm having following traceback:(

Traceback (most recent call last): File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/core/handlers/exception.py", line 56, in inner response = get_response(request) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/core/handlers/base.py", line 220, in _get_response response = response.render() File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/response.py", line 114, in render self.content = self.rendered_content File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/rest_framework/response.py", line 70, in rendered_content ret = renderer.render(self.data, accepted_media_type, context) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/rest_framework/renderers.py", line 166, in render return template.render(context, request=request) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/backends/django.py", line 61, in render return self.template.render(context) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/base.py", line 175, in render return self._render(context) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/base.py", line 167, in _render return self.nodelist.render(context) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/base.py", line 1005, in render return SafeString("".join([node.render_annotated(context) for node in self])) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/base.py", line 1005, in return SafeString("".join([node.render_annotated(context) for node in self])) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/base.py", line 966, in render_annotated return self.render(context) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/django/template/library.py", line 237, in render output = self.func(*resolved_args, **resolved_kwargs) File "/home/wojciech/PycharmProjects/thumbnail/virtual/lib/python3.10/site-packages/rest_framework/templatetags/rest_framework.py", line 81, in render_form return renderer.render(serializer.data, None, {'style': style}) AttributeError: 'str' object has no attribute 'data' [08/Mar/2023 09:59:08] "POST /uploadimage/ HTTP/1.1" 500 115861

ruddra · Accepted Answer · 2023-03-08 10:49:19Z

2

For the form, you need to add enctype information to bind the file to the form, like this:

<form method="post" enctype="multipart/form-data">
{% csrf_token %}
        {% render_form serializer %}

    <input type="submit" value="Wyślij">
</form>

For the actual problem regarding str object has no attribute data, DRF documentation mentions that:

Django rest framework looks for render_form template tag, to render Serializer.

The error is happening because in the html file it is looking for rendering the serializer using render_form tag. Since you are passing the serializer as serializer context variable, you need to send the serializer in post method like this:

   if serializer.is_valid():
        serializer.save(uploaded_by=self.request.user)
        return Response({"serializer":serializer})

If you do not want to render the form again, I suggest either redirect it to a different url where you get the same response in JSON format using JSONRenderer. If you intend to render in the response in HTML, then I would put another context variable, like this:

# view
if serializer.is_valid():
    serializer.save(uploaded_by=self.request.user)
    return Response({"serializer":serializer, "data": serializer.data})

# template
{% if data %}
    {{ data }}
{{ endif }}
<form method="post" enctype="multipart/form-data">
{% csrf_token %}
        {% render_form serializer %}

    <input type="submit" value="Wyślij">
</form>

edited Mar 8, 2023 at 10:49

answered Mar 7, 2023 at 11:05

ruddra

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11 Comments

djangobeginner Over a year ago

Thanks that works! Can you advise why Im getting ` return renderer.render(serializer.data, None, {'style': style}) AttributeError: 'str' object has no attribute 'data'` as return instead of link?

ruddra Over a year ago

without the enctype, you would not get the file stream in the views, instead you will get a string, hence the error happened.

djangobeginner Over a year ago

unfortunately enctype helped with uploading images from browser, but it returns error at the end. serializer.data = {'image_url': '/media/media/airplane.jpg-1678205283', 'expiring_within': 4444} but this line return Response(serializer.data, status=status.HTTP_200_OK) returns return renderer.render(serializer.data, None, {'style': style}) AttributeError: 'str' object has no attribute 'data'

ruddra Over a year ago

@djangobeginner where do you use serializer.data = {'image_url': '/media/media/airplane.jpg-1678205283', 'expiring_within': 4444} ?

djangobeginner Over a year ago

in ` def post(self, request): serializer = PostSerializer(data=request.data) if serializer.is_valid(): serializer.save(uploaded_by=self.request.user) return Response(serializer.data, status=status.HTTP_200_OK)`

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