Django rename uploaded file: append specific string at the end - django

Question

I'm restricting the upload button to allow only csv files.
I need help please to append _hello at the end of each file uploaded by the user, but before the extension. (e.g. user_file_name.csv becomes automatically user_file_name_hello.csv)
Optional: I'd like the original file to be first renamed automatically, then saved to my uploads directory.
models.py
from django.db import models
# validation method to check if file is csv
from django.core.exceptions import ValidationError
def validate_file_extension(value):
if not value.name.endswith('.csv'):
raise ValidationError(u'Only CSV files allowed.')
# Create your models here.
class user_file(models.Model):
user_file_csv = models.FileField(upload_to='documents/user_files/', validators=[validate_file_extension])
forms.py
from django import forms
from .models import user_file
from django.forms import FileInput
class user_file_form(forms.ModelForm):
class Meta:
model = user_file
widgets = {'user_file_csv': FileInput(attrs={'accept': 'text/csv'})}
fields = ('user_file_csv',)
Thank you!

Answer 1

Maybe you need something like this:
class FileUploadUtil:
#staticmethod
def my_files_path(instance, filename):
name, file_extention = os.path.splitext(filename)
name = 'prefix-{}-{}-sufix.{}'.format(name, instance.id, file_extention)
return "my_files/{}".format(name)
class MyModel(models.Model):
# Other fields
# ...
my_file = models.FileField(max_length=300, upload_to=FileUploadUtil.my_files_path)

Answer 2

Optional: I'd like the original file to be first renamed automatically, then saved to my uploads directory.
You can override save() method. Check here
Django document
Maybe You need decorator.
from pathlib import Path
def rename_helper(path: str, append_text: str):
stem, suffix = Path(path).stem, Path(path).suffix
return f"{stem}{append_text}{suffix}"
def rename_previous_image(func):
""" return wrapper object """
def wrapper(*args, **kwargs):
self = args[0]
model = type(self)
previous_obj = model.objects.filter(pk=self.pk)
if previous_obj.exists():
old_name_with_path = Path(str(previous_obj[0].user_file_csv))
Path.rename(old_name_with_path , rename_helper(path=old_name_with_path , append_text="_hello"))
return func(*args, **kwargs)
return wrapper
And, You can decorate your model save() method.
class MyModel(models.Model):
# Other fields
# ...
my_file = models.FileField(max_length=300, upload_to=FileUploadUtil.my_files_path)
#rename_previous_image
def save(self, **kwargs):
super(user_file, self).save(**kwargs) # You must add This row.
besides,
recommend rename your user_file class
like UserFile
Check This PEP 8
Have a good day.