Django rename uploaded file: append specific string at the end

• 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!

Maybe you need something like this:

class FileUploadUtil:

    @staticmethod
    def my_files_path(instance, filename):
        name, file_extention = os.path.splitext(filename)
        name = 'prefix-{}-{}-suffix.{}'.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)