How does Django rename uploaded files? - django

Question

If upload a file image.png from a web browser, a new file named image.png will appear in the upload directory on the server.
If I then upload another file named image.png (same name), a new file named image_aj642zm.png will appear in the upload directory on the server.
Then, if I upload another file named image.png (again the same name), a new file named image_z6z2BaQ.png will appear in the upload directory on the server.
What method does Django use to rename the uploaded file if a file with that name already exists in the upload directory?
(i.e. where does the extra _aj642zm and _z6z2BaQ come from?)
The usual set-up:
In models.py:
from django.db import models
class Image(models.Model):
image = models.ImageField(upload_to='uploads/')
In forms.py:
from django import forms
from .models import Image
class ImageForm(forms.ModelForm):
class Meta:
model = Image
fields = ['image']
In views.py:
from django.shortcuts import render, redirect
from .forms import ImageForm
def upload_image(request):
if request.method == 'POST':
form = ImageForm(request.POST, request.FILES)
if form.is_valid():
form.save()
return redirect('index')
else:
form = ImageForm()
return render(request, 'upload_file.html', {'form': form})

Answer 1

Django default Storage class method called get_available_name
# If the filename already exists, add an underscore and a random 7
# character alphanumeric string (before the file extension, if one
# exists) to the filename until the generated filename doesn't exist.
# Truncate original name if required, so the new filename does not
# exceed the max_length.
Django by default saves object by its name but if object with that name already exists adds up underscore and 7 random chars as quoted in code comment
Also as addition to this Django Storage class method get_valid_name parses up file name before and replaces all spaces with underscores and removes all chars that are not unicode, alpha, dash, underscore or dot
re.sub(r'(?u)[^-\w.]', '', s)