src/cpl_query/_extension/iterable.py

@@ -1,9 +1,10 @@
-from typing import Optional, Callable
+from typing import Optional, Callable, Union
 
 from cpl_query._extension.ordered_iterable import OrderedIterable
 from cpl_query.extension.ordered_iterable_abc import OrderedIterableABC
 from .._query.all_query import all_query
 from .._query.any_query import any_query
+from .._query.avg_query import avg_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
@@ -23,6 +24,9 @@ class Iterable(IterableABC):
     def all(self, func: Callable) -> bool:
         return all_query(self, func)
 
+    def average(self, t: type, func: Callable) -> Union[int, float, complex]:
+        return avg_query(self, t, func)
+
     def first(self) -> any:
         return first_query(self)
 

src/cpl_query/_query/avg_query.py

@@ -0,0 +1,22 @@
+from typing import Callable, Union
+
+from cpl_query.exceptions import InvalidTypeException, WrongTypeException
+from cpl_query.extension.iterable_abc import IterableABC
+
+
+def avg_query(_list: IterableABC, _t: type, _func: Callable) -> Union[int, float, complex]:
+    average = 0
+    count = len(_list)
+
+    if _t != int and _t != float and _t != complex:
+        raise InvalidTypeException()
+
+    for element in _list:
+        value = _func(element)
+        if type(value) != _t:
+            raise WrongTypeException()
+
+        average += value
+
+    return average / count
+

src/cpl_query/exceptions.py

@@ -0,0 +1,6 @@
+class InvalidTypeException(Exception):
+    pass
+
+
+class WrongTypeException(Exception):
+    pass

src/cpl_query/extension/iterable_abc.py

@@ -1,5 +1,5 @@
 from abc import ABC, abstractmethod
-from typing import Optional, Callable
+from typing import Optional, Callable, Union
 
 
 class IterableABC(ABC, list):
@@ -14,6 +14,9 @@ class IterableABC(ABC, list):
     @abstractmethod
     def all(self, func: Callable) -> bool: pass
 
+    @abstractmethod
+    def average(self, t: type, func: Callable) -> Union[int, float, complex]: pass
+
     @abstractmethod
     def first(self) -> any: pass
 

src/cpl_query/tests/query_test.py

@@ -3,6 +3,7 @@ import unittest
 from random import randint
 
 from cpl.utils import String
+from cpl_query.exceptions import InvalidTypeException, WrongTypeException
 from cpl_query.extension.list import List
 from cpl_query.tests.models import User, Address
 
@@ -59,6 +60,28 @@ class QueryTest(unittest.TestCase):
         self.assertTrue(res)
         self.assertFalse(n_res)
 
+    def test_avg(self):
+        avg = 0
+        for user in self._tests:
+            avg += user.address.nr
+
+        avg = avg / len(self._tests)
+        res = self._tests.average(int, lambda u: u.address.nr)
+
+        self.assertEqual(res, avg)
+
+    def test_avg_invalid(self):
+        def _():
+            res = self._tests.average(str, lambda u: u.address.nr)
+
+        self.assertRaises(InvalidTypeException, _)
+
+    def test_avg_wrong(self):
+        def _():
+            res = self._tests.average(int, lambda u: u.address.street)
+
+        self.assertRaises(WrongTypeException, _)
+
     def test_first(self):
         results = []
         for user in self._tests: