Merge pull request #37 from PickwickSoft/feature/add-sum-operation-to…

…-numerical-stream

Add `sum()` operation to numerical streams

pystreamapi/_streams/numeric/__numeric_base_stream.py

@@ -75,6 +75,13 @@ def range(self) -> Union[float, int, None]:
         self._trigger_exec()
         return max(self._source) - min(self._source) if len(self._source) > 0 else None
 
+    @abstractmethod
+    def sum(self) -> Union[float, int, None]:
+        """
+        Calculates the sum of all items of a numerical stream
+        :return: The sum, can be int or float
+        """
+
     def third_quartile(self) -> Union[float, int, None]:
         """
         Calculates the third quartile of a numerical Stream

pystreamapi/_streams/numeric/__parallel_numeric_stream.py

@@ -12,6 +12,12 @@ def mean(self) -> Union[float, int, None]:
         self._trigger_exec()
         return self.__sum() / len(self._source) if len(self._source) > 0 else None
 
+    def sum(self) -> Union[float, int, None]:
+        """Calculates the sum of values"""
+        self._trigger_exec()
+        _sum = self.__sum()
+        return 0 if _sum == [] else _sum
+
     def __sum(self):
         """Parallel sum method"""
         self._set_parallelizer_src()

pystreamapi/_streams/numeric/__sequential_numeric_stream.py

@@ -11,3 +11,8 @@ def mean(self) -> Union[float, int, None]:
         """Calculates mean of values"""
         self._trigger_exec()
         return sum(self._source) / len(self._source) if len(self._source) > 0 else None
+
+    def sum(self) -> Union[float, int, None]:
+        """Calculates the sum of values"""
+        self._trigger_exec()
+        return sum(self._source)

tests/test_numeric_stream_implementation.py

@@ -23,3 +23,11 @@ def test_mean_empty(self):
     def test_mean_negative(self):
         result = self.stream([-1, -2, -3, -4, -5]).mean()
         self.assertEqual(result, -3)
+
+    def test_sum(self):
+        result = self.stream([1, 2, 3, 4, 5]).sum()
+        self.assertEqual(result, 15)
+
+    def test_sum_empty(self):
+        result = self.stream([]).sum()
+        self.assertEqual(result, 0)