Add type hints to methods. Add tests for invalid values.

README.md

@@ -43,7 +43,6 @@ In [8]: regions.countries_by_subregion('053')
 Out[8]: ['AU', 'NZ', 'NF']
 ```
 
-
 ## Development
 
 To contribute to this library, first checkout the code. Then create a new virtual environment:

django_countries_regions/__init__.py

@@ -2,7 +2,7 @@
 from django_countries_regions.regions import REGIONS, SUBREGIONS
 
 
-def country_region(country_code, region=True):
+def country_region(country_code: str, region: bool = True) -> str | None:
     """Return a UN M49 region code for a country.
 
     Extends django-countries by adding a .region method to the Country field.
@@ -12,18 +12,24 @@ def country_region(country_code, region=True):
     :return: String. UN M49 region code.
     """
     code_to_use = "un_region_code" if region else "un_subregion_code"
-    return COUNTRY_REGIONS[country_code][code_to_use]
+    try:
+        return COUNTRY_REGIONS[country_code][code_to_use]
+    except KeyError:
+        return None
 
 
-def country_subregion(country_code):
+def country_subregion(country_code: str) -> str | None:
     """Return a UN M49 sub-region code for a country.
 
     Extends django-countries by adding a .subregion method to the Country field.
 
     :param country_code: Two-letter ISO country code.
     :return: String. UN M49 sub-region code.
     """
-    return country_region(country_code, region=False)
+    try:
+        return country_region(country_code, region=False)
+    except KeyError:
+        return None
 
 
 class Regions():
@@ -32,7 +38,7 @@ class Regions():
     that region.
     """
 
-    def countries_by_region(self, region_code, region=True):
+    def countries_by_region(self, region_code: str, region: bool = True) -> str | None:
         """Return a list of country codes found within a region.
 
         :param region_code: UN M49 region code.
@@ -41,39 +47,51 @@ def countries_by_region(self, region_code, region=True):
         """
         if region_code:
             if region:
-                return REGIONS[region_code]["countries"]
+                try:
+                    return REGIONS[region_code]["countries"]
+                except KeyError:
+                    return None
             else:
                 return SUBREGIONS[region_code]["countries"]
         return None
 
-    def countries_by_subregion(self, region_code):
+    def countries_by_subregion(self, region_code: str) -> str | None:
         """Return a list of country codes found within a sub-region
 
         :param region_code: UN M49 sub-region code.
         :return: List of two-letter ISO country codes.
         """
         if region_code:
-            return self.countries_by_region(region_code, region=False)
+            try:
+                return self.countries_by_region(region_code, region=False)
+            except KeyError:
+                return None
         return None
 
-    def region_name(self, region_code):
+    def region_name(self, region_code: str) -> str | None:
         """Return the region name
 
         :param region_code: UN M49 region code.
         :return: String
         """
         if region_code:
-            return REGIONS[region_code]["name"]
+            try:
+                return REGIONS[region_code]["name"]
+            except KeyError:
+                return None
         return None
 
-    def subregion_name(self, region_code):
+    def subregion_name(self, region_code: str) -> str | None:
         """Return the region name
 
         :param region_code: UN M49 sub-region code.
         :return: String
         """
         if region_code:
-            return SUBREGIONS[region_code]["name"]
+            try:
+                return SUBREGIONS[region_code]["name"]
+            except KeyError:
+                return None
         return None
 
 

tests/test_django_countries_regions.py

@@ -20,6 +20,14 @@ def test_country_subregion(self):
         query = Country("AF").subregion
         self.assertEqual(query, "034")
 
+    def test_invalid_country_region(self):
+        query = Country("ZZ").region
+        self.assertIsNone(query)
+
+    def test_invalid_country_subregion(self):
+        query = Country("ZZ").subregion
+        self.assertIsNone(query)
+
 
 class TestRegions(TestCase):
     def test_countries_by_region(self):
@@ -37,3 +45,19 @@ def test_region_name(self):
     def test_subregion_name(self):
         query = regions.subregion_name("053")
         self.assertEqual(query, "Australia and New Zealand")
+
+    def test_invalid_countries_by_region(self):
+        query = regions.countries_by_region("900")
+        self.assertIsNone(query)
+
+    def test_invalid_countries_by_subregion(self):
+        query = regions.countries_by_subregion("999")
+        self.assertIsNone(query)
+
+    def test_invalid_region_name(self):
+        query = regions.region_name("900")
+        self.assertIsNone(query)
+
+    def test_invalid_subregion_name(self):
+        query = regions.subregion_name("999")
+        self.assertIsNone(query)