The camera angle in Blender can be set both in millimeters – the Focal Length parameter, and in degrees – the Field of View parameter.
To get the Field of View in degrees from the Focal Length value in millimeters, we can use the following formula:
FoV – camera Field of View in radians
W – camera Sensor Width in millimeters
S – camera Focal Length in millimeters
For example, for the selected camera with a Focal Length of 60 mm and a Sensor Width of 36 mm, the camera angle in degrees will be:
math.degrees(2 * math.atan(bpy.context.object.data.sensor_width /(2 * bpy.context.object.data.lens)))