Add sum.py with summation function

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sum.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+"""
+A simple module for summing numbers.
+"""
+
+def sum_numbers(numbers):
+    """
+    Sum a list of numbers.
+
+    Args:
+        numbers: List of numbers (int or float)
+
+    Returns:
+        Sum of the numbers
+    """
+    return sum(numbers)
+
+def main():
+    """Example usage of sum_numbers function."""
+    # Example 1: Sum integers
+    int_list = [1, 2, 3, 4, 5]
+    result = sum_numbers(int_list)
+    print(f"Sum of {int_list} = {result}")
+
+    # Example 2: Sum floats
+    float_list = [1.5, 2.5, 3.5]
+    result = sum_numbers(float_list)
+    print(f"Sum of {float_list} = {result}")
+
+    # Example 3: Empty list
+    empty_list = []
+    result = sum_numbers(empty_list)
+    print(f"Sum of {empty_list} = {result}")
+
+if __name__ == "__main__":
+    main()