Add test and code

src/maorganizer/datawrangling.py

@@ -60,6 +60,10 @@ class Attendancelist:
 
         return Attendancelist({Person(name) for name in df[cname]})
 
+    @property
+    def n_attendees(self):
+        return len(self.participants)
+
     def to_df(self):
         return pd.DataFrame(
             [

tests/test_attendancelist.py

@@ -32,3 +32,10 @@ def test_attendance_list_updates_correctly():
             }
         )
     ) == Attendancelist(participants={Person("lord crawfish")})
+
+
+def test_attendancelist_has_correct_n_attendees():
+    assert (
+        Attendancelist({Person("zaphod beeblebrox"), Person("ford prefix")}).n_attendees
+        == 2
+    )