Addresses problem when too many excluded users were being excluded

lms/djangoapps/gradebook/models.py

@@ -30,7 +30,7 @@ class StudentGradebook(TimeStampedModel):
         unique_together = (('user', 'course_id'),)
 
     @classmethod
-    def generate_leaderboard(cls, course_key, user_id=None, count=3, exclude_users=None):
+    def generate_leaderboard(cls, course_key, user_id=None, count=3, exclude_users=[]):
         """
         Assembles a data set representing the Top N users, by grade, for a given course.
         Optionally provide a user_id to include user-specific info.  For example, you
@@ -62,25 +62,19 @@ class StudentGradebook(TimeStampedModel):
         data['course_count'] = 0
         data['queryset'] = []
 
-        total_user_count = CourseEnrollment.users_enrolled_in(course_key).count()
-        if total_user_count:
+        enrolled_users_not_excluded = CourseEnrollment.users_enrolled_in(course_key).exclude(id__in=exclude_users)
+        total_user_count = enrolled_users_not_excluded.count()
 
+        if total_user_count:
             # Generate the base data set we're going to work with
             queryset = StudentGradebook.objects.select_related('user')\
-                .filter(course_id__exact=course_key, user__is_active=True)
-            gradebook_user_count = len(queryset)
-            if gradebook_user_count:
-
-                # Remove any users who should not be considered for the statistics
-                if exclude_users:
-                    total_user_count = total_user_count - len(exclude_users)
-                    queryset = queryset.exclude(user__in=exclude_users)
+                .filter(course_id__exact=course_key, user__is_active=True, user__in=enrolled_users_not_excluded)
             gradebook_user_count = len(queryset)
 
             if gradebook_user_count:
                 # Calculate the class average
                 course_avg = queryset.aggregate(Avg('grade'))['grade__avg']
-                    if course_avg is not None and gradebook_user_count < total_user_count:
+                if course_avg is not None:
                     # Take into account any ungraded students (assumes zeros for grades...)
                     course_avg = course_avg / total_user_count * gradebook_user_count