src/cpl_query/_extension/iterable.py

@@ -6,6 +6,7 @@ from .._query.all_query import all_query
 from .._query.any_query import any_query
 from .._query.avg_query import avg_query
 from .._query.contains_query import contains_query
+from .._query.count_query import count_query
 from .._query.first_query import first_or_default_query, first_query
 from .._query.for_each_query import for_each_query
 from .._query.order_by import order_by_query, order_by_descending_query
@@ -31,6 +32,9 @@ class Iterable(IterableABC):
     def contains(self, value: object) -> bool:
         return contains_query(self, value)
 
+    def count(self, func: Callable = None) -> int:
+        return count_query(self, func)
+
     def first(self) -> any:
         return first_query(self)
 

src/cpl_query/_query/count_query.py

@@ -0,0 +1,15 @@
+from collections import Callable
+
+from cpl_query._query.where_query import where_query
+from cpl_query.exceptions import ArgumentNoneException, ExceptionArgument
+from cpl_query.extension.iterable_abc import IterableABC
+
+
+def count_query(_list: IterableABC, _func: Callable = None) -> int:
+    if _list is None:
+        raise ArgumentNoneException(ExceptionArgument.list)
+
+    if _func is None:
+        return len(_list)
+
+    return len(where_query(_list, _func))

src/cpl_query/extension/iterable_abc.py

@@ -20,6 +20,9 @@ class IterableABC(ABC, list):
     @abstractmethod
     def contains(self, value: object) -> bool: pass
 
+    @abstractmethod
+    def count(self, func: Callable) -> int: pass
+
     @abstractmethod
     def first(self) -> any: pass
 

src/cpl_query/tests/query_test.py

@@ -83,6 +83,10 @@ class QueryTest(unittest.TestCase):
         self.assertTrue(self._tests.contains(self._t_user))
         self.assertFalse(self._tests.contains(User("Test", None)))
 
+    def test_count(self):
+        self.assertEqual(len(self._tests), self._tests.count())
+        self.assertEqual(1, self._tests.count(lambda u: u == self._t_user))
+
     def test_first(self):
         results = []
         for user in self._tests: