Add dot_interpolate function

dimagi/utils/tests/__init__.py

@@ -11,4 +11,5 @@
 }
 
 from lazy_attachment_doc import *
-from dates import *
+from dates import *
+from xpath import *

dimagi/utils/tests/xpath.py

@@ -0,0 +1,18 @@
+from django.test import TestCase
+from ..xpath import dot_interpolate
+
+
+class DotInterpolateTest(TestCase):
+
+    def testRegex(self):
+        replacement = "@case_id stuff"
+        cases = [
+            ('./lmp < 570.5', '%s/lmp < 570.5'),
+            ('stuff ./lmp < 570.', 'stuff %s/lmp < 570.'),
+            ('.53 < hello.', '.53 < hello%s'),
+        ]
+        for case in cases:
+            self.assertEqual(
+                dot_interpolate(replacement, case[0]),
+                case[1] % replacement
+            )

dimagi/utils/xpath.py

@@ -0,0 +1,10 @@
+import re
+
+
+def dot_interpolate(xpath, context):
+    """
+    Replaces non-decimal dots in `context` with `xpath`
+    """
+    pattern = r'(\D|^)\.(\D|$)'
+    repl = '\g<1>%s\g<2>' % xpath
+    return re.sub(pattern, repl, context)