aggregation field operations added

common_helper_mongo/__init__.py

 from .gridfs import overwrite_file
-from .aggregate import get_objects_and_count_of_occurrence
+from .aggregate import get_objects_and_count_of_occurrence, get_field_average, get_field_sum, get_field_execute_operation
 
 __all__ = [
            'overwrite_file',
-           'get_objects_and_count_of_occurrence'
+           'get_objects_and_count_of_occurrence',
+           'get_field_average',
+           'get_field_sum',
+           'get_field_execute_operation'
         ]

common_helper_mongo/aggregate.py

@@ -17,3 +17,23 @@ def get_objects_and_count_of_occurrence(collection, object_path, unwind=False, m
     result = list(collection.aggregate(pipeline))
     logging.debug(result)
     return result
+
+
+def get_field_sum(collection, object_path, match=None):
+    return get_field_execute_operation("$sum", collection, object_path, match=match)
+
+
+def get_field_average(collection, object_path, match=None):
+    return get_field_execute_operation("$avg", collection, object_path, match=match)
+
+
+def get_field_execute_operation(operation, collection, object_path, match=None):
+    pipeline = []
+    if match is not None:
+        pipeline.append({"$match": match})
+    pipeline.append({"$group": {"_id": "null", "total": {operation: object_path}}})
+    tmp = collection.aggregate(pipeline)
+    result = 0
+    for item in tmp:
+        result = item['total']
+    return result

tests/test_aggregate.py

-from common_helper_mongo.aggregate import get_objects_and_count_of_occurrence
+from common_helper_mongo.aggregate import get_objects_and_count_of_occurrence,\
+    get_field_sum, get_field_average
 import unittest
 from tests.base_class_database_test import MongoDbTest
 
@@ -24,7 +25,16 @@ class TestAggregate(MongoDbTest):
         result = get_objects_and_count_of_occurrence(self.test_collection, "$test_txt", unwind="False", match={"test_int": 0})
         self.assertEqual(len(result), 1, "number of results not correct")
         self.assertEqual(result[0]['_id'], "item 0")
-        print(result)
+
+    def test_get_field_sum(self):
+        self.add_simple_test_data()
+        result = get_field_sum(self.test_collection, "$test_int")
+        self.assertEqual(result, 45)
+
+    def test_get_field_avg(self):
+        self.add_simple_test_data()
+        result = get_field_average(self.test_collection, "$test_int")
+        self.assertEqual(result, 4.5)
 
 
 if __name__ == "__main__":