[1.5.x] Fixed #19829 -- Fixed index lookups for NumPy arrays in templates.

Backport of 7d5e35cdb46124e2471

django/template/base.py

@@ -756,7 +756,7 @@ class Variable(object):
             for bit in self.lookups:
                 try:  # dictionary lookup
                     current = current[bit]
-                except (TypeError, AttributeError, KeyError):
+                except (TypeError, AttributeError, KeyError, ValueError):
                     try:  # attribute lookup
                         current = getattr(current, bit)
                     except (TypeError, AttributeError):

tests/regressiontests/templates/tests.py

@@ -54,6 +54,12 @@ except ImportError as e:
     else:
         raise
 
+# NumPy installed?
+try:
+    import numpy
+except ImportError:
+    numpy = False
+
 from . import filters
 
 #################################
@@ -1649,6 +1655,17 @@ class Templates(TestCase):
             'verbatim-tag05': ('{% verbatim %}{% endverbatim %}{% verbatim %}{% endverbatim %}', {}, ''),
             'verbatim-tag06': ("{% verbatim special %}Don't {% endverbatim %} just yet{% endverbatim special %}", {}, "Don't {% endverbatim %} just yet"),
         }
+
+        if numpy:
+            tests.update({
+                # Numpy's array-index syntax allows a template to access a certain item of a subscriptable object.
+                'numpy-array-index01': ("{{ var.1 }}", {"var": numpy.array(["first item", "second item"])}, "second item"),
+
+                # Fail silently when the array index is out of range.
+                'numpy-array-index02': ("{{ var.5 }}", {"var": numpy.array(["first item", "second item"])}, ("", "INVALID")),
+            })
+
+
         return tests
 
 class TemplateTagLoading(unittest.TestCase):