diff --git a/src/my_project/interviews/top_150_questions_round_19/number_of_one_bits.py b/src/my_project/interviews/top_150_questions_round_19/number_of_one_bits.py
new file mode 100644
index 00000000..f1cfb550
--- /dev/null
+++ b/src/my_project/interviews/top_150_questions_round_19/number_of_one_bits.py
@@ -0,0 +1,6 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution:
+    def hammingWeight(self, n: int) -> int: 
+        return bin(n).count('1')
\ No newline at end of file
diff --git a/tests/test_150_questions_round_19/test_number_of_one_bits_round_19.py b/tests/test_150_questions_round_19/test_number_of_one_bits_round_19.py
new file mode 100644
index 00000000..4130ada0
--- /dev/null
+++ b/tests/test_150_questions_round_19/test_number_of_one_bits_round_19.py
@@ -0,0 +1,11 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_19\
+.number_of_one_bits import Solution
+
+class NumberOfOnesTestCase(unittest.TestCase):
+
+    def test_number_of_ones(self):
+        solution = Solution()
+        output = solution.hammingWeight(n=11)
+        target = 3
+        self.assertEqual(output, target)
\ No newline at end of file