diff --git a/journals/models.py b/journals/models.py index 7b310e4377c00a774b9819d6812c757a19d2d93e..60d245706428e48f5974260e269da3ef485be0b1 100644 --- a/journals/models.py +++ b/journals/models.py @@ -63,7 +63,9 @@ class Journal(models.Model): duration = Publication.objects.filter( in_issue__in_volume__in_journal=self).aggregate( avg=Avg(F('publication_date') - F('submission_date')))['avg'] - return duration.total_seconds() / 86400 + if duration: + return duration.total_seconds() / 86400 + return 0 def citation_rate(self, tier=None): """ @@ -111,7 +113,9 @@ class Volume(models.Model): duration = Publication.objects.filter( in_issue__in_volume=self).aggregate( avg=Avg(F('publication_date') - F('submission_date')))['avg'] - return duration.total_seconds() / 86400 + if duration: + return duration.total_seconds() / 86400 + return 0 def citation_rate(self, tier=None): """ @@ -191,7 +195,9 @@ class Issue(models.Model): duration = Publication.objects.filter( in_issue=self).aggregate( avg=Avg(F('publication_date') - F('submission_date')))['avg'] - return duration.total_seconds() / 86400 + if duration: + return duration.total_seconds() / 86400 + return 0 def citation_rate(self, tier=None): """