[Django]-Django ImageField change file name on upload

Django 1.7 and newer won’t make migration with function like this. Based on answer by @miki725 and this ticket, you need to make your function like this:

import os
from uuid import uuid4
from django.utils.deconstruct import deconstructible

@deconstructible
class UploadToPathAndRename(object):

    def __init__(self, path):
        self.sub_path = path

    def __call__(self, instance, filename):
        ext = filename.split('.')[-1]
        # get filename
        if instance.pk:
            filename = '{}.{}'.format(instance.pk, ext)
        else:
            # set filename as random string
            filename = '{}.{}'.format(uuid4().hex, ext)
        # return the whole path to the file
        return os.path.join(self.sub_path, filename)

FileField(upload_to=UploadToPathAndRename(os.path.join(MEDIA_ROOT, 'upload', 'here'), ...)

You can replace the string your assigning to upload_to with a callable as described in the docs. However, I suspect the primary key may not be available at the point the upload_to parameter is used.

By default Django keeps the original name of the uploaded file but more than likely you will want to rename it to something else (like the object’s id). Luckily, with ImageField or FileField of Django forms, you can assign a callable function to the upload_to parameter to do the renaming. For example:

from django.db import models
from django.utils import timezone
import os
from uuid import uuid4

def path_and_rename(instance, filename):
    upload_to = 'photos'
    ext = filename.split('.')[-1]
    # get filename
    if instance.pk:
        filename = '{}.{}'.format(instance.pk, ext)
    else:
        # set filename as random string
        filename = '{}.{}'.format(uuid4().hex, ext)
    # return the whole path to the file
    return os.path.join(upload_to, filename)

and in models field:

class CardInfo(models.Model):
    ...
    photo = models.ImageField(upload_to=path_and_rename, max_length=255, null=True, blank=True)

In this example, every image that is uploaded will be rename to the CardInfo object’s primary key which is id_number.

Another option, as following this answer https://stackoverflow.com/a/15141228/3445802, we found the issue when we need return path with %Y/%m/%d, example:

FileField(upload_to=path_and_rename('upload/here/%Y/%m/%d'), ...)

so, we handle it with this:

FileField(upload_to=path_and_rename('upload/here/{}'.format(time.strftime("%Y/%m/%d"))), ...)

Makesure the module time has been imported.

I do have a more customizable implementation of Aidan Ewen’s solution.

What’s new?

• You can send the fields you want to use in the filenames as a list (as pre-ordered)
• ^ one of them must be unique
• ^ else, this list must include (at least one of) the tuple of unique together fields
• ^ else, fields you sent are will be ignored and will use the uuid4 as filename

example 1:

image = models.ImageField(upload_to=PathAndRename('images/').wrapper)

filename = {pk}.{ext}
# default is pk for filenames

example 2:

name = models.CharField(max_length=20)  # not unique
image = models.ImageField(upload_to=PathAndRename('images/', ['name']).wrapper)

filename = {uuid4}.{ext}
# if given fields are did not accepted will use the uuid4

example 3:

name = models.CharField(max_length=20, unique=True)
no = models.CharField(max_length=10)
image = models.ImageField(upload_to=PathAndRename('images/', ['name','no']).wrapper)

filename = {name}_{no}.{ext}
# one unique field is enough to use all of the given fields in the filename

example 4:

name = models.CharField(max_length=20)  # not unique
no = models.CharField(max_length=10)  # not unique
image = models.ImageField(upload_to=PathAndRename('images/', ['name','no']).wrapper)

class Meta:
    unique_together = ('name', 'no')
    # (('name', 'no'),) is acceptable too or multiple unique togethers

filename = {name}_{no}.{ext}
# if one of the unique together fields exists in the given fields, will use all of the given fields in the filename

I may be forgot to give some more examples but you can understand from the code below:

class PathAndRename:
    """
    fields to use for naming, order is important
    """

    def __init__(self, path, fields_to_use=('pk',)):
        self.path = path
        self.fields_to_use = fields_to_use

    def wrapper(self, instance, filename):
        # multiple extensions
        ext = '.'.join(filename.split('.')[1:])

        # check the uniqueness of the fields given for filename
        if self.is_any_unique_exist(instance):
            # if any unique field exist in the given list
            # create filename by using given field values
            filename = '{}.{}'.format(self.get_filename_by_fields(instance), ext)
        # else check the existence of at least one unique together
        elif self.is_any_unique_together_exist(instance):
            # create filename by using given field values
            filename = '{}.{}'.format(self.get_filename_by_fields(instance), ext)
        # if any unique or unique together not exists
        else:
            # then create a filename by using uuid4
            filename = '{}.{}'.format(uuid4().hex, ext)

        # return the whole path to the file
        return os.path.join(self.path, filename)

    def is_any_unique_exist(self, instance):
        if 'pk' in self.fields_to_use:
            return True
        return any([instance._meta.get_field(field).unique for field in self.fields_to_use if hasattr(instance, field)])

    def is_any_unique_together_exist(self, instance):
        if hasattr(instance._meta, 'unique_together'):
            if isinstance(instance._meta.unique_together, (list, tuple)):
                for uniques in instance._meta.unique_together:
                    # if any one of the unique together set is exists in the fields to use
                    if all(map(lambda field: field in self.fields_to_use, uniques)):
                        return True
            else:
                if all(map(lambda field: field in self.fields_to_use, instance._meta.unique_together)):
                    return True
        return False

    def get_filename_by_fields(self, instance):
        return '_'.join([str(getattr(instance, field)) for field in self.fields_to_use])

WARNING: Every method-based solution to this upload_to problem is problematic for preformed migration files when you abandon using these solutions. If you use these solutions for a while and then delete them, the old migrations will fail because of the unexistence of these methods. (of course, you can fix this problem by modifying the old migration files)

I changed the accepted answer a little bit for easy understanding.

def wrapper(instance, filename):
    ext = filename.split('.')[-1]
    # get filename
    if instance.pk:
        filename = '{}.{}'.format(instance.pk, ext) # do instance.username 
                                                    # if you want to save as username
    else:
        # set filename as random string
        filename = '{}.{}'.format(uuid4().hex, ext)
    # return the whole path to the file
    return os.path.join('path/to/save/', filename)

image = models.ImageField(upload_to=wrapper, default="/user.png", null=True, blank=True)