diff --git a/exposurejapan/database.py b/exposurejapan/database.py
index ed9f6cff29075524455ff8a60f9f5e01cbdf3730..914a11918285909e6eebf4093265ecd2fad288da 100644
--- a/exposurejapan/database.py
+++ b/exposurejapan/database.py
@@ -25,8 +25,29 @@ import pandas
 logger = logging.getLogger(__name__)
 
 
+def add_element_and_get_index(element, element_list):
+    """
+    Checks if an element is in a list and adds it to the list if not.
+    Returns the index of the element in the list.
+
+    Args:
+        element (str):
+            Element to be added to the list
+        element_list (list):
+            List to add the element to
+
+    Returns:
+         Index of inserted element in the list
+    """
+
+    if element not in element_list:
+        element_list.append(element)
+    return element_list.index(element)
+
+
 class JapanDatabase(SpatialiteDatabase):
-    """The JapanDatabase class represents a Spatialite database for the Japan
+    """
+    The JapanDatabase class represents a Spatialite database for the Japan
     exposure model. It is derived from the generic Database class.
 
     Args:
@@ -314,17 +335,13 @@ class JapanDatabase(SpatialiteDatabase):
                 continue
             district_id = result[0]
 
-            # Get ID of building type
-            building_type = row["Type of building"]
-            if building_type not in building_type_list:
-                building_type_list.append(building_type)
-            building_type_id = building_type_list.index(building_type)
-
-            # Get ID of number of stories
-            story_number = row["Stories of building"]
-            if story_number not in story_number_list:
-                story_number_list.append(story_number)
-            story_number_id = story_number_list.index(story_number)
+            # Get ID of building type and number of stories
+            building_type_id = add_element_and_get_index(
+                row["Type of building"], building_type_list
+            )
+            story_number_id = add_element_and_get_index(
+                row["Stories of building"], story_number_list
+            )
 
             # Insert dwelling numbers for each construction material
             for material_id in range(5):
@@ -362,17 +379,13 @@ class JapanDatabase(SpatialiteDatabase):
                 continue
             district_id = result[0]
 
-            # Get ID of building type
-            building_type = row["Type of building"]
-            if building_type not in building_type_list:
-                building_type_list.append(building_type)
-            building_type_id = building_type_list.index(building_type)
-
-            # Get ID of number of stories
-            story_number = row["Stories of building"]
-            if story_number not in story_number_list:
-                story_number_list.append(story_number)
-            story_number_id = story_number_list.index(story_number)
+            # Get ID of building type and number of stories
+            building_type_id = add_element_and_get_index(
+                row["Type of building"], building_type_list
+            )
+            story_number_id = add_element_and_get_index(
+                row["Stories of building"], story_number_list
+            )
 
             # Insert building numbers for each construction material
             for material_index in range(3):