Changed filenames to UUID4 which are thrown into a single directory. Added auto-delete for changed / deleted PlaceImages.

source/lostplaces/lostplaces_app/models.py

@@ -1,4 +1,9 @@
+import os
+import uuid
+
 from django.db import models
+from django.dispatch import receiver
+from django.utils.translation import ugettext_lazy as _
 
 # Create your models here.
 
@@ -13,9 +18,44 @@ class Place (models.Model):
         return self.name
 
 class PlaceImage (models.Model):
-    filename = models.ImageField(upload_to='places/%Y/%m/', max_length=50)
+    filename = models.ImageField(
+        upload_to=lambda instance, filename: 'places/' + str(uuid.uuid4()),
+        max_length=50
+        )
     place = models.ForeignKey(Place, on_delete=models.CASCADE, related_name='images')
     description = models.TextField(blank=True)
 
     def __str__(self):
         return ' '.join([self.place.name, str(self.pk)])
+
+# These two auto-delete files from filesystem when they are unneeded:
+
+@receiver(models.signals.post_delete, sender=PlaceImage)
+def auto_delete_file_on_delete(sender, instance, **kwargs):
+    """
+    Deletes file from filesystem
+    when corresponding `PlaceImage` object is deleted.
+    """
+    if instance.filename:
+        if os.path.isfile(instance.filename.path):
+            os.remove(instance.filename.path)
+
+@receiver(models.signals.pre_save, sender=PlaceImage)
+def auto_delete_file_on_change(sender, instance, **kwargs):
+    """
+    Deletes old file from filesystem
+    when corresponding `PlaceImage` object is updated
+    with new file.
+    """
+    if not instance.pk:
+        return False
+
+    try:
+        old_file = PlaceImage.objects.get(pk=instance.pk).filename
+    except PlaceImage.DoesNotExist:
+        return False
+
+    new_file = instance.filename
+    if not old_file == new_file:
+        if os.path.isfile(old_file.path):
+            os.remove(old_file.path)