FileField - Django Models

FileField is a file-upload field. Before uploading files, one needs to specify a lot of settings so that file is securely saved and can be retrieved in a convenient manner. The default form widget for this field is a ClearableFileInput. Syntax

field_name = models.FileField(upload_to=None, max_length=254, **options)

FileField has an optional arguments:

FileField.upload_to

This attribute provides a way of setting the upload directory and file name, and can be set in two ways. In both cases, the value is passed to the Storage.save() method. If you specify a string value, it may contain strftime() formatting, which will be replaced by the date/time of the file upload (so that uploaded files don’t fill up the given directory). For example: Python3 1==

class MyModel(models.Model):

    # file will be uploaded to MEDIA_ROOT / uploads
    upload = models.FileField(upload_to ='uploads/')

    # or...
    # file will be saved to MEDIA_ROOT / uploads / 2015 / 01 / 30
    upload = models.FileField(upload_to ='uploads/% Y/% m/% d/')

If you are using the default FileSystemStorage, the string value will be appended to your MEDIA_ROOT path to form the location on the local filesystem where uploaded files will be stored. If you are using different storage, check that storage’s documentation to see how it handles upload_to. upload_to may also be a callable, such as a function. This will be called to obtain the upload path, including the filename. This callable must accept two arguments and return a Unix-style path (with forward slashes) to be passed along to the storage system. The two arguments are:

Argument	Description
instance	An instance of the model where the FileField is defined. More specifically, this is a particular instance where the current file is being attached.
filename	The filename that was originally given to the file. This may or may not be taken into account when determining the final destination path

For example: Python3 1==

def user_directory_path(instance, filename):

    # file will be uploaded to MEDIA_ROOT / user_<id>/<filename>
    return 'user_{0}/{1}'.format(instance.user.id, filename)

class MyModel(models.Model):
    upload = models.FileField(upload_to = user_directory_path)

Django Model FileField Explanation

Illustration of FileField using an Example. Consider a project named geeksforgeeks having an app named geeks.

Refer to the following articles to check how to create a project and an app in Django.

• How to Create a Basic Project using MVT in Django?
• How to Create an App in Django ?

Enter the following code into models.py file of geeks app. Python3

from django.db import models
from django.db.models import Model
# Create your models here.

class GeeksModel(Model):
    geeks_field = models.FileField()

Add the geeks app to INSTALLED_APPS Python3

# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'geeks',
]

Now when we run makemigrations command from the terminal,

Python manage.py makemigrations

A new folder named migrations would be created in geeks directory with a file named 0001_initial.py Python3

# Generated by Django 2.2.5 on 2019-09-25 06:00

from django.db import migrations, models

class Migration(migrations.Migration):

    initial = True

    dependencies = [
    ]

    operations = [
        migrations.CreateModel(
            name ='GeeksModel',
            fields =[
                ('id', 
                  models.AutoField(
                  auto_created = True,
                  primary_key = True,
                  serialize = False, 
                  verbose_name ='ID'
                )),
                ('geeks_field', models.FileField()),
            ],
        ),
    ]

Now run,

Python manage.py migrate

Thus, an geeks_field FileField is created when you run migrations on the project. It is a field to store any kind of file in the database.

How to use FileField ?

FileField is used for storing files into the database. One can any type of file in FileField. Let's try storing an image in the model created above.

• To start creating instances of model, create an admin account by using the following command.

  Python manage.py createsuperuser

• Enter a username, email and a secure password. Then in your browser enter the following URL.

  http://localhost:8000/admin/

  
• Go to add in front of Geeks Models.
• Choose the file you want to upload and click on save. Now let's check it in admin server. We have created an instance of GeeksModel.

Field Options

Field Options are the arguments given to each field for applying some constraint or imparting a particular characteristic to a particular Field. For example, adding an argument null = True to FileField will enable it to store empty values for that table in relational database. Here are the field options and attributes that a FileField can use.

Field Options	Description
Null	If True, Django will store empty values as NULL in the database. Default is False.
Blank	If True, the field is allowed to be blank. Default is False.
db_column	The name of the database column to use for this field. If this isn’t given, Django will use the field’s name.
Default	The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created.
help_text	Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form.
primary_key	If True, this field is the primary key for the model.
editable	If False, the field will not be displayed in the admin or any other ModelForm. They are also skipped during model validation. Default is True.
error_messages	The error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override.
help_text	Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form.
verbose_name	A human-readable name for the field. If the verbose name isn’t given, Django will automatically create it using the field’s attribute name, converting underscores to spaces.
validators	A list of validators to run for this field. See the validators documentation for more information.
Unique	If True, this field must be unique throughout the table.