use r to prefix regex

analytic_structure.py

@@ -235,7 +235,7 @@
 
         ans_dict = self.get_dimensions_names(model)
 
-        regex = '{pre}(\d+)_{suf}'.format(pre=prefix, suf=suffix)
+        regex = r'{pre}(\d+)_{suf}'.format(pre=prefix, suf=suffix)
         match_fct = re.compile(regex).search
         matches = filter(None, map(match_fct, fields.keys()))
 
@@ -290,7 +290,7 @@
         ans_dict = self.get_dimensions_names(model)
         found_fields = {slot: False for slot in ans_dict}
 
-        regex = '{pre}(\d+)_{suf}'.format(pre=prefix, suf=suffix)
+        regex = r'{pre}(\d+)_{suf}'.format(pre=prefix, suf=suffix)
         path = "//field[re:match(@name, '{0}')]".format(regex)
         ns = {"re": "http://exslt.org/regular-expressions"}