src/cpl_query/_extension/iterable.py

@@ -7,6 +7,7 @@ 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.distinct_query import distinct_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
@@ -35,6 +36,11 @@ class Iterable(IterableABC):
     def count(self, func: Callable = None) -> int:
         return count_query(self, func)
 
+    def distinct(self, func: Callable) -> IterableABC:
+        res = distinct_query(self, func)
+        res.__class__ = Iterable
+        return res
+
     def first(self) -> any:
         return first_query(self)
 

src/cpl_query/_query/distinct_query.py

@@ -0,0 +1,24 @@
+from collections import Callable
+
+from cpl_query.exceptions import ArgumentNoneException, ExceptionArgument
+from cpl_query.extension.iterable_abc import IterableABC
+
+
+def distinct_query(_list: IterableABC, _func: Callable) -> IterableABC:
+    if _list is None:
+        raise ArgumentNoneException(ExceptionArgument.list)
+
+    if _func is None:
+        raise ArgumentNoneException(ExceptionArgument.func)
+
+    result = IterableABC()
+    known_values = []
+    for element in _list:
+        value = _func(element)
+        if value in known_values:
+            continue
+
+        known_values.append(value)
+        result.append(element)
+
+    return result

src/cpl_query/extension/iterable_abc.py

@@ -23,6 +23,9 @@ class IterableABC(ABC, list):
     @abstractmethod
     def count(self, func: Callable) -> int: pass
 
+    @abstractmethod
+    def distinct(self, func: Callable) -> 'IterableABC': pass
+
     @abstractmethod
     def first(self) -> any: pass
 
@@ -33,13 +36,13 @@ class IterableABC(ABC, list):
     def for_each(self, func: Callable): pass
 
     @abstractmethod
-    def order_by(self, func: Callable): pass
+    def order_by(self, func: Callable) -> 'IterableABC': pass
 
     @abstractmethod
-    def order_by_descending(self, func: Callable): pass
+    def order_by_descending(self, func: Callable) -> 'IterableABC': pass
 
     @abstractmethod
-    def single(self): pass
+    def single(self) -> any: pass
 
     @abstractmethod
     def single_or_default(self) -> Optional[any]: pass

src/cpl_query/tests/query_test.py

@@ -87,6 +87,10 @@ class QueryTest(unittest.TestCase):
         self.assertEqual(len(self._tests), self._tests.count())
         self.assertEqual(1, self._tests.count(lambda u: u == self._t_user))
 
+    def test_distinct(self):
+        res = self._tests.distinct(lambda u: u.address.nr).where(lambda u: u.address.nr == 5)
+        self.assertEqual(1, len(res))
+
     def test_first(self):
         results = []
         for user in self._tests: