I did a slider in a own menu to increase or decrease selection using sharp edge angle, but I can only increase not decrease.
def update_sharpangle(self, context):
bpy.ops.mesh.edges_select_sharp(sharpness=radians(context.scene.sharpangle))
bpy.types.Scene.sharpangle=bpy.props.FloatProperty(default=70, min=0, max=90,precision=1,update=update_sharpangle)