Allow customising ChoiceField blank display value

rest_framework/fields.py

@@ -509,12 +509,16 @@ class ChoiceField(WritableField):
                             'the available choices.'),
     }
 
-    def __init__(self, choices=(), *args, **kwargs):
+    def __init__(self, choices=(), blank_display_value=None, *args, **kwargs):
         self.empty = kwargs.pop('empty', '')
         super(ChoiceField, self).__init__(*args, **kwargs)
         self.choices = choices
         if not self.required:
-            self.choices = BLANK_CHOICE_DASH + self.choices
+            if blank_display_value is None:
+                blank_choice = BLANK_CHOICE_DASH
+            else:
+                blank_choice = [('', blank_display_value)]
+            self.choices = blank_choice + self.choices
 
     def _get_choices(self):
         return self._choices

rest_framework/tests/test_fields.py

@@ -706,6 +706,15 @@ class ChoiceFieldTests(TestCase):
         f = serializers.ChoiceField(required=False, choices=SAMPLE_CHOICES)
         self.assertEqual(f.choices, models.fields.BLANK_CHOICE_DASH + SAMPLE_CHOICES)
 
+    def test_blank_choice_display(self):
+        blank = 'No Preference'
+        f = serializers.ChoiceField(
+            required=False,
+            choices=SAMPLE_CHOICES,
+            blank_display_value=blank,
+        )
+        self.assertEqual(f.choices, [('', blank)] + SAMPLE_CHOICES)
+
     def test_invalid_choice_model(self):
         s = ChoiceFieldModelSerializer(data={'choice': 'wrong_value'})
         self.assertFalse(s.is_valid())