Add strptime template function (#3950)

homeassistant/helpers/template.py

@@ -1,4 +1,5 @@
 """Template helper methods for rendering strings with HA data."""
+from datetime import datetime
 import json
 import logging
 import re
@@ -386,6 +387,14 @@ def timestamp_utc(value):
         return value
 
 
+def strptime(string, fmt):
+    """Parse a time string to datetime."""
+    try:
+        return datetime.strptime(string, fmt)
+    except (ValueError, AttributeError):
+        return string
+
+
 def fail_when_undefined(value):
     """Filter to force a failure when the value is undefined."""
     if isinstance(value, jinja2.Undefined):
@@ -420,3 +429,4 @@ ENV.globals['now'] = dt_util.now
 ENV.globals['utcnow'] = dt_util.utcnow
 ENV.globals['as_timestamp'] = dt_util.as_timestamp
 ENV.globals['relative_time'] = dt_util.get_age
+ENV.globals['strptime'] = strptime

tests/helpers/test_template.py

@@ -1,4 +1,5 @@
 """Test Home Assistant template helper methods."""
+from datetime import datetime
 import unittest
 from unittest.mock import patch
 
@@ -122,6 +123,32 @@ class TestHelpersTemplate(unittest.TestCase):
                 template.Template('{{ %s | multiply(10) | round }}' % inp,
                                   self.hass).render())
 
+    def test_strptime(self):
+        """Test the parse timestamp method."""
+        tests = [
+            ('2016-10-19 15:22:05.588122 UTC',
+             '%Y-%m-%d %H:%M:%S.%f %Z', None),
+            ('2016-10-19 15:22:05.588122+0100',
+             '%Y-%m-%d %H:%M:%S.%f%z', None),
+            ('2016-10-19 15:22:05.588122',
+             '%Y-%m-%d %H:%M:%S.%f', None),
+            ('2016-10-19', '%Y-%m-%d', None),
+            ('2016', '%Y', None),
+            ('15:22:05', '%H:%M:%S', None),
+            ('1469119144', '%Y', '1469119144'),
+            ('invalid', '%Y', 'invalid')
+        ]
+
+        for inp, fmt, expected in tests:
+            if expected is None:
+                expected = datetime.strptime(inp, fmt)
+
+            temp = '{{ strptime(\'%s\', \'%s\') }}' % (inp, fmt)
+
+            self.assertEqual(
+                str(expected),
+                template.Template(temp, self.hass).render())
+
     def test_timestamp_custom(self):
         """Test the timestamps to custom filter."""
         tests = [