apply_modifiers.py

import bpy

def execute(self, context):   

    target_obj = context.active_object
    tool_objs = [o for o in context.selected_objects if o != target_obj]

    BOOL = 'BOOLEAN'
    # first add them.
    for obj in tool_objs:
        bool_mod = target_obj.modifiers.new(name='difference_' + obj.name, type=BOOL)
        bool_mod.operation = 'DIFFERENCE'
        bool_mod.object = obj
    
    # then apply them individually.
    for modifier in target_obj.modifiers:
        bpy.ops.object.modifier_apply(modifier=modifier.name)

execute(None, bpy.context)