Update sphere.py

src/geometry/sphere.py

@@ -1,21 +1,40 @@
-from math import pi
-
-
-def calculate_surface_area(r):
-    """ 
-    Calculate the surface area of a sphere. 
-
-    This uses the standard mathematical calculation: 
-
-    $4\pi r ^2$
-
-    Parameters
-    ----------
-    r : float, the radius 
-
-    Returns
-    -------
-    float : the surface area of the sphere
-    """
-    surface_area = 4 * pi * r **2
-    return surface_area
+from math import pi
+
+def calculate_volume(r):
+  """ 
+  Calculate the volume of a sphere. 
+
+  This uses the standard mathematical calculation: 
+
+  $\(4/3) pi r ^3$
+
+  Parameters
+  ----------
+  r : float, the radius 
+
+  Returns
+  -------
+  float : the volume of the sphere
+  """
+  volume = (4/3) * pi * r **3
+  return volume
+
+
+def calculate_surface_area(r):
+    """ 
+    Calculate the surface area of a sphere. 
+
+    This uses the standard mathematical calculation: 
+
+    $4\pi r ^2$
+
+    Parameters
+    ----------
+    r : float, the radius 
+
+    Returns
+    -------
+    float : the surface area of the sphere
+    """
+    surface_area = 4 * pi * r **2
+    return surface_area