[Django]-Dynamic File Path in Django

https://docs.djangoproject.com/en/stable/ref/models/fields/#django.db.models.FileField.upload_to

def upload_path_handler(instance, filename):
    return "user_{id}/{file}".format(id=instance.user.id, file=filename)

class Car(models.Model):
    ...
    photo = models.ImageField(upload_to=upload_path_handler, storage=fs)

There is a warning in the docs, but it shouldn’t affect you since we’re after the User ID and not the Car ID.

In most cases, this object will not
have been saved to the database yet,
so if it uses the default AutoField,
it might not yet have a value for its
primary key field.

You can use lambda function as below, take note that if instance is new then it won’t have the instance id, so use something else:

logo = models.ImageField(upload_to=lambda instance, filename: 'directory/images/{0}/{1}'.format(instance.owner.id, filename))

My solution is not elegant, but it works:

In the model, use a the standard function that will need the id/pk

def directory_path(instance, filename):
    return 'files/instance_id_{0}/{1}'.format(instance.pk, filename)

in views.py save the form like this:

f=form.save(commit=False)
ftemp1=f.filefield
f.filefield=None
f.save()
#And now that we have crated the record we can add it
f.filefield=ftemp1
f.save()

It worked for me.
Note: My filefield in models and allowed for Null values. Null=True

Well very late to the party but this one works for me.

def content_file_name(instance, filename):
    upload_dir = os.path.join('uploads',instance.albumname)
    if not os.path.exists(upload_dir):
        os.makedirs(upload_dir)
    return os.path.join(upload_dir, filename)

Model like this only

class Album(models.Model):
    albumname = models.CharField(max_length=100)
    audiofile = models.FileField(upload_to=content_file_name)

There are two solutions on DjangoSnippets

1. Two-stage save: https://djangosnippets.org/snippets/1129/
2. Prefetch the ID (PostgreSQL only): https://djangosnippets.org/snippets/2731/

This guy has a way to do dynamic path. The idea is to set your favourite storage and customise “upload_to()” parameter with a function.

Hope this helps.

I found out a different solution, which is dirty, but it works. You should create a new dummy model, which is self synchronized with the original one. I’m not proud of this, but didn’t find another solution. In my case I want to upload files, and store each in a directory named after the model id (because I’ll generate there more files).

the model.py

class dummyexperiment(models.Model):
  def __unicode__(self):
    return str(self.id)

class experiment(models.Model):
  def get_exfile_path(instance, filename):
    if instance.id == None:
      iid = instance.dummye.id
    else:
      iid = instance.id
    return os.path.join('experiments', str(iid), filename)

  exfile = models.FileField(upload_to=get_exfile_path)

  def save(self, *args, **kwargs):
    if self.id == None:
      self.dummye = dummyexperiment()
      self.dummye.save()
    super(experiment, self).save(*args, **kwargs)

I’m very new in python and in django, but it seems like ok for me.

another solution:

def get_theme_path(instance, filename):
  id = instance.id
  if id == None:
    id = max(map(lambda a:a.id,Theme.objects.all())) + 1
  return os.path.join('experiments', str(id), filename)

As the primary key (id) may not be available if the model instance was not saved to the database yet, I wrote my FileField subclasses which move the file on model save, and a storage subclass which removes the old files.

Storage:

class OverwriteFileSystemStorage(FileSystemStorage):
    def _save(self, name, content):
        self.delete(name)
        return super()._save(name, content)

    def get_available_name(self, name):
        return name

    def delete(self, name):
        super().delete(name)

        last_dir = os.path.dirname(self.path(name))

        while True:
            try:
                os.rmdir(last_dir)
            except OSError as e:
                if e.errno in {errno.ENOTEMPTY, errno.ENOENT}:
                    break

                raise e

            last_dir = os.path.dirname(last_dir)

FileField:

def tweak_field_save(cls, field):
    field_defined_in_this_class = field.name in cls.__dict__ and field.name not in cls.__bases__[0].__dict__

    if field_defined_in_this_class:
        orig_save = cls.save

        if orig_save and callable(orig_save):
            assert isinstance(field.storage, OverwriteFileSystemStorage), "Using other storage than '{0}' may cause unexpected behavior.".format(OverwriteFileSystemStorage.__name__)

            def save(self, *args, **kwargs):
                if self.pk is None:
                    orig_save(self, *args, **kwargs)

                    field_file = getattr(self, field.name)

                    if field_file:
                        old_path = field_file.path
                        new_filename = field.generate_filename(self, os.path.basename(old_path))
                        new_path = field.storage.path(new_filename)
                        os.makedirs(os.path.dirname(new_path), exist_ok=True)
                        os.rename(old_path, new_path)
                        setattr(self, field.name, new_filename)

                    # for next save
                    if len(args) > 0:
                        args = tuple(v if k >= 2 else False for k, v in enumerate(args))

                    kwargs['force_insert'] = False
                    kwargs['force_update'] = False

                orig_save(self, *args, **kwargs)

            cls.save = save


def tweak_field_class(orig_cls):
    orig_init = orig_cls.__init__

    def __init__(self, *args, **kwargs):
        if 'storage' not in kwargs:
            kwargs['storage'] = OverwriteFileSystemStorage()

        if orig_init and callable(orig_init):
            orig_init(self, *args, **kwargs)

    orig_cls.__init__ = __init__

    orig_contribute_to_class = orig_cls.contribute_to_class

    def contribute_to_class(self, cls, name):
        if orig_contribute_to_class and callable(orig_contribute_to_class):
            orig_contribute_to_class(self, cls, name)

        tweak_field_save(cls, self)

    orig_cls.contribute_to_class = contribute_to_class

    return orig_cls


def tweak_file_class(orig_cls):
    """
    Overriding FieldFile.save method to remove the old associated file.
    I'm doing the same thing in OverwriteFileSystemStorage, but it works just when the names match.
    I probably want to preserve both methods if anyone calls Storage.save.
    """

    orig_save = orig_cls.save

    def new_save(self, name, content, save=True):
        self.delete(save=False)

        if orig_save and callable(orig_save):
            orig_save(self, name, content, save=save)

    new_save.__name__ = 'save'
    orig_cls.save = new_save

    return orig_cls


@tweak_file_class
class OverwriteFieldFile(models.FileField.attr_class):
    pass


@tweak_file_class
class OverwriteImageFieldFile(models.ImageField.attr_class):
    pass


@tweak_field_class
class RenamedFileField(models.FileField):
    attr_class = OverwriteFieldFile


@tweak_field_class
class RenamedImageField(models.ImageField):
    attr_class = OverwriteImageFieldFile

and my upload_to callables look like this:

def user_image_path(instance, filename):
    name, ext = 'image', os.path.splitext(filename)[1]

    if instance.pk is not None:
        return os.path.join('users', os.path.join(str(instance.pk), name + ext))

    return os.path.join('users', '{0}_{1}{2}'.format(uuid1(), name, ext))

MEDIA_ROOT/
   /company_Company1/company.png
                    /shop_Shop1/shop.png
                               /bikes/bike.png


def photo_path_company(instance, filename):
# file will be uploaded to MEDIA_ROOT/company_<name>/
    return 'company_{0}/{1}'.format(instance.name, filename)

class Company(models.Model):
    name = models.CharField()
    photo = models.ImageField(max_length=255, upload_to=photo_path_company)

def photo_path_shop(instance, filename):
# file will be uploaded to MEDIA_ROOT/company_<name>/shop_<name>/
    parent_path = instance.company._meta.get_field('photo').upload_to(instance.company, '')
    return parent_path + 'shop_{0}/{1}'.format(instance.name, filename)

class Shop(models.Model):
    name = models.CharField()
    photo = models.ImageField(max_length=255, upload_to=photo_path_shop)

def photo_path_bike(instance, filename):
    # file will be uploaded to MEDIA_ROOT/company_<name>/shop_<name>/bikes/
    parent_path = instance.shop._meta.get_field('photo').upload_to(instance.shop, '')
    return parent_path + 'bikes/{0}'.format(filename)


class Bike(models.Model):
    name = models.CharField()
    photo = models.ImageField(max_length=255, upload_to=photo_path_bike)

You can override model’s save method:

def save_image(instance, filename):
    instance_id = f'{instance.id:03d}'  # 001
    return f'{instance_id}-{filename.lower()}'  # 001-foo.jpg

class Resource(models.Model):
    photo = models.ImageField(upload_to=save_image)

   def save(self, *args, **kwargs):
        if self.id is None:
            photo = self.photo
            self.photo = None
            super().save(*args, **kwargs)
            self.photo = photo
            if 'force_insert' in kwargs:
                kwargs.pop('force_insert')
        super().save(*args, **kwargs)

The method will be

def user_directory_path(field_name):

    def upload_path(instance, filename):
        year = datetime.now().year
        name, ext = instance.user, os.path.splitext(filename)[1]
        return f'photos/{year}/{instance._meta.model_name}s/{instance.user}/{field_name}_{name}{ext}'

    return upload_path

And in your models you can have as many ImageField as you like. example

photo = models.ImageField(upload_to=user_directory_path('photo'), null=True, blank=True,)
passport_photo = models.ImageField(upload_to=user_directory_path('passport_photo'), null=True, blank=True,)