Move duration methods in to utils for use elsewhere in the project.

core/templatetags/duration.py

@@ -1,54 +1,56 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
-from datetime import timedelta
-
 from django import template
 
+from core.utils import duration_parts, duration_string as d_string
+
 
 register = template.Library()
 
 
 @register.filter
 def duration_string(duration):
-    h, m, s = _get_hms(duration)
-
-    duration = ''
-    if h > 0:
-        duration = '{} hour{}'.format(h, 's' if h > 1 else '')
-    if m > 0:
-        duration += '{}{} minute{}'.format(
-            '' if duration is '' else ', ', m, 's' if m > 1 else '')
-    if s > 0:
-        duration += '{}{} second{}'.format(
-            '' if duration is '' else ', ', s, 's' if s > 1 else '')
-
-    return duration
+    """Format a duration (e.g. "2 hours, 3 minutes, 35 seconds")."""
+    if not duration:
+        return ''
+    try:
+        return d_string(duration)
+    except (ValueError, TypeError):
+        return ''
 
 
 @register.filter
 def hours(duration):
-    h, m, s = _get_hms(duration)
-    return h
+    """Return "hours" portion of a duration."""
+    if not duration:
+        return 0
+    try:
+        h, m, s = duration_parts(duration)
+        return h
+    except (ValueError, TypeError):
+        return 0
 
 
 @register.filter
 def minutes(duration):
-    h, m, s = _get_hms(duration)
-    return m
+    """Return "minutes" portion of a duration."""
+    if not duration:
+        return 0
+    try:
+        h, m, s = duration_parts(duration)
+        return m
+    except (ValueError, TypeError):
+        return 0
 
 
 @register.filter
 def seconds(duration):
-    h, m, s = _get_hms(duration)
-    return s
-
-
-def _get_hms(duration):
-    """Get hours, minutes and seconds from a timedelta."""
-    if not isinstance(duration, timedelta):
-        return 0, 0, 0
-    h, remainder = divmod(duration.seconds, 3600)
-    h += duration.days * 24
-    m, s = divmod(remainder, 60)
-    return h, m, s
+    """Return "seconds" portion of a duration."""
+    if not duration:
+        return 0
+    try:
+        h, m, s = duration_parts(duration)
+        return s
+    except (ValueError, TypeError):
+        return 0

core/utils.py

@@ -23,3 +23,31 @@ def timer_stop(timer_id, end=None):
     timer_instance = Timer.objects.get(id=timer_id)
     timer_instance.end = end
     timer_instance.save()
+
+
+def duration_string(duration):
+    """Format hours, minutes and seconds in a human-friendly way (e.g. "2
+    hours, 25 minutes, 31 seconds")"""
+    h, m, s = duration_parts(duration)
+
+    duration = ''
+    if h > 0:
+        duration = '{} hour{}'.format(h, 's' if h > 1 else '')
+    if m > 0:
+        duration += '{}{} minute{}'.format(
+            '' if duration is '' else ', ', m, 's' if m > 1 else '')
+    if s > 0:
+        duration += '{}{} second{}'.format(
+            '' if duration is '' else ', ', s, 's' if s > 1 else '')
+
+    return duration
+
+
+def duration_parts(duration):
+    """Get hours, minutes and seconds from a timedelta."""
+    if not isinstance(duration, timezone.timedelta):
+        raise TypeError('Duration provided must be a timedetla')
+    h, remainder = divmod(duration.seconds, 3600)
+    h += duration.days * 24
+    m, s = divmod(remainder, 60)
+    return h, m, s