Bezier_handle_adjuster.py

import bpy 
from mathutils import Vector

def adjust_bezier_controls(instruction='average'):

    '''
    W -> resize longest
    W -> resize shortest
    W -> normalize
    W -> average
    '''

    bpy.ops.object.mode_set(mode = 'OBJECT')
    ao = bpy.context.active_object
    if not ao.type == 'CURVE':
        return

    active_spline = ao.data.splines.active
    for s in active_spline.bezier_points:
        if not (s.select_control_point and s.select_left_handle and s.select_right_handle):
            continue
        else:
            
            distance_1 = (s.co - s.handle_left).length
            distance_2 = (s.co - s.handle_right).length
            
            if instruction == 'average':
                avg = (distance_1 + distance_2) / 2
                s.handle_left = s.co.lerp(s.handle_left, avg / distance_1)
                s.handle_right = s.co.lerp(s.handle_right, avg / distance_2)
            # break
    bpy.ops.object.mode_set(mode = 'EDIT')
    


adjust_bezier_controls(instruction='average')