Django - Type Error: expected string or bytes-like object
<p>I've seen other questions about this error but none of them were able to help so I figured I make on myself. As per the title, I keep getting this type error and I have run out of ideas as to why it is occurring. </p>

<p>I am making an app that involves a Gallery object that adds Photo objects. What I have been specifically working on recently was a zip_upload function in order to add photos from a .zip file. I have tried Photologue but I am deciding to handle everything myself for multiple reasons. Actually, I referred to Photologue a lot when writing it so there any many similarities. Here is my code(left out unimportant details) and traceback:</p>

<p>Models:</p>

<pre><code>from django.utils.timezone import now

class ImageModel(models.Model):
  image = models.ImageField('image',max_length=100,upload_to='photos')
  class Meta:
      abstract = True

class Photo(ImageModel):
  title = models.CharField('title',max_length=250,unique=True)
  date_added = models.DateTimeField('date added',default=now)
  objects = PhotoQuerySet.as_manager()

class Gallery(models.Model):
  title = models.CharField('title',max_length=250,unique=True)
  photos = models.ManyToManyField(Photo,
             related_name='gallery',verbose_name='photos', blank=True)
  objects = GalleryQuerySet.as_manager()
</code></pre>

<p>Admin page:</p>

<pre><code>class GalleryAdmin(admin.ModelAdmin):

    def get_urls(self):
        urls = super(GalleryAdmin, self).get_urls()
        add_urls = [
            url(r'^upload_zip/$',
                self.admin_site.admin_view(self.upload_zip),
                name='upload_zip')
        ]
        return add_urls + urls

    def upload_zip(self,request):
        context = {
            'app_label': self.model._meta.app_label,
            'opts': self.model._meta,
        }

        # Handle form request
        if request.method == 'POST':
            form = UploadZipForm(request.POST, request.FILES)
            if form.is_valid():
                form.save(request=request)
                return HttpResponseRedirect('..')
        else:
            form = UploadZipForm()
        context['form'] = form
        context['adminform'] = helpers.AdminForm(form,
                         list([(None{'fields':form.base_fields})]),{})
        return render(
            request,'admin/inv_app/gallery/upload_zip.html',context)
</code></pre>

<p>Form:</p>

<pre><code>class UploadZipForm(forms.Form):
  zip_file = forms.FileField()
  title = forms.CharField(label='Title',required=False)
  gallery = forms.ModelChoiceField(Gallery.objects.all(),
        label='Gallery',required=False,)

  # left out methods that check if zip_file is valid and titles have 
  # not been used by other Gallery objects

  def save(self, request=None, zip_file=None):
    if not zip_file:
        zip_file = self.cleaned_data['zip_file']
      zip = zipfile.ZipFile(zip_file,'r')
      count = 1
      if self.cleaned_data['gallery']:
          logger.debug('Using pre-existing gallery.')
          gallery = self.cleaned_data['gallery']
      else:
          logger.debug(
            force_text('Creating new gallery "{0}".')
                 .format(self.cleaned_data['title']))
          gallery = Gallery.objects.create(
            title=self.cleaned_data['title'],
            slug=slugify(self.cleaned_data['title']),)
      found_image = False
    for filename in sorted(zip.namelist()):
        _, file_extension = os.path.splitext(filename)
        file_extension = file_extension.lower()
        if not file_extension or file_extension != '.jpg':
            continue
        # check file is not subfolder

        data = zip.read(filename)

        # check file is not empty, assign title to photo

        contentfile = ContentFile(data)
        photo.image.save(filename, contentfile)
        # I believe the error is produced here ^
        photo.save()
        gallery.photos.add(photo)
    zip.close()
</code></pre>

<p>Traceback:</p>

<pre><code>File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/core/handlers/base.py" in get_response
  response = self.process_exception_by_middleware(e, request)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/core/handlers/base.py" in get_response 
  response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/utils/decorators.py" in _wrapped_view
  response = view_func(request, *args, **kwargs)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  response = view_func(request, *args, **kwargs)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/contrib/admin/sites.py" in inner
  return view(request, *args, **kwargs)
File "/Users/Lucas/Documents/inventory-master/inv_app/admin.py" in upload_zip
  form.save(request=request)
File "/Users/Lucas/Documents/inventory-master/inv_app/forms.py" in save
  photo.image.save(filename, contentfile)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/fields/files.py" in save
  self.instance.save()
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/base.py" in save
  force_update=force_update, update_fields=update_fields)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/base.py" in save_base
  updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/base.py" in _save_table
  result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/base.py" in _do_insert
  using=using, raw=raw)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/manager.py" in manager_method
  return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/query.py" in _insert
  return query.get_compiler(using=using).execute_sql(return_id)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/sql/compiler.py" in execute_sql
  for sql, params in self.as_sql():
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/sql/compiler.py" in as_sql
  for obj in self.query.objs
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/sql/compiler.py" in &lt;listcomp&gt;
  for obj in self.query.objs
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/sql/compiler.py" in &lt;listcomp&gt;
  [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields]
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/sql/compiler.py" in prepare_value
  value = field.get_db_prep_save(value, connection=self.connection)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/fields/__init__.py" in get_db_prep_save
  prepared=False)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/fields/__init__.py" in get_db_prep_value
  value = self.get_prep_value(value)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/fields/__init__.py" in get_prep_value
  value = super(DateTimeField, self).get_prep_value(value)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/fields/__init__.py" in get_prep_value
  return self.to_python(value)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/db/models/fields/__init__.py" in to_python
  parsed = parse_datetime(value)
File "/Users/Lucas/Documents/python_envs/inventory/lib/python3.5/site-packages/django/utils/dateparse.py" in parse_datetime
  match = datetime_re.match(value)

Exception Type: TypeError at /admin/inv_app/gallery/upload_zip/
Exception Value: expected string or bytes-like object
</code></pre>

<p>I am relatively new to web dev so I'm sure I'm missing something minuscule or obvious. Please help! </p>

<p>Well I was able to solve it on my own!</p>

<p>My problem was the way I was overriding the Photo model's save method:</p>

<pre><code>def save(self, *args, **kwargs):
    if self.slug is None:
        self.slug = slugify(self.title)
    super(Photo, self).save(*args, **kwargs)
</code></pre>

<p>For some reason it was not saving properly so removing it fixed the bug and it works the way it should now. I figured I did not really need to override it so I did not need to replace it! I am realizing I did not post this portion of the model in my original question so that is my mistake for not trying to completely understand the error before posting.</p>

python django