Rename files on upload

schoolapps/helper.py

+import os
+from uuid import uuid4
+
+
+def path_and_rename(instance, filename):
+    upload_to = 'menus'
+    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)

schoolapps/mealplan/migrations/0002_auto_20181129_1743.py

+# Generated by Django 2.0.7 on 2018-11-29 16:43
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('mealplan', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='mealplan',
+            name='pdf',
+            field=models.FileField(upload_to='menus/'),
+        ),
+    ]

schoolapps/mealplan/migrations/0003_auto_20181129_1747.py

+# Generated by Django 2.0.7 on 2018-11-29 16:47
+
+from django.db import migrations, models
+import helper
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('mealplan', '0002_auto_20181129_1743'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='mealplan',
+            name='pdf',
+            field=models.FileField(upload_to=helper.path_and_rename),
+        ),
+    ]

schoolapps/mealplan/models.py

 from django.db import models
 
-
 # Create your models here.
+from helper import path_and_rename
+
+
 class MealPlan(models.Model):
     calendar_week = models.IntegerField()
     year = models.IntegerField()
-    pdf = models.FileField(upload_to="menus/")
+    pdf = models.FileField(upload_to=path_and_rename)
 
     def __str__(self):
         return "KW {}/{}".format(self.calendar_week, self.year)