How to add and use renamed Mirror modifier with Python?

Question

In this code for 2.8, that works, I am creating a mirror modifier assigned to a cube.

import bpy

OB = bpy.context.selected_objects[0]
bpy.ops.object.modifier_add(type='MIRROR')
bpy.ops.object.mode_set(mode='OBJECT')
bpy.ops.object.empty_add(type='CUBE', view_align=False, location=(bpy.context.scene.cursor_location))
OA = bpy.context.selected_objects[0]
bpy.context.object.name = "Mirror Axes"
bpy.ops.transform.resize(value=(0.01, 1, 1), constraint_axis=(True, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='ENABLED', proportional_edit_falloff='SMOOTH', proportional_size=0.00439353)
OB.modifiers["Mirror"].mirror_object = OA 

The problem is that I cannot use this script multiple times correctly because of this part:

OB.modifiers["Mirror"].mirror_object = OA 

The object will always have a modifier named "Mirror" and if I use this script two times the modifier named "Mirror" will always be the first one and I want it to be the same modifier.

So it needs to be more something like this:

OB = bpy.context.selected_objects[0]
bpy.ops.object.modifier_add(type='MIRROR')
         ***RENAME MIRROR MODIFIER TO A CUSTOM NAME THAT CHANGE EACH TIME***
bpy.ops.object.mode_set(mode='OBJECT')
bpy.ops.object.empty_add(type='CUBE', view_align=False, location=(bpy.context.scene.cursor_location))
OA = bpy.context.selected_objects[0]
bpy.context.object.name = "Mirror Axes"
bpy.ops.transform.resize(value=(0.01, 1, 1), constraint_axis=(True, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='ENABLED', proportional_edit_falloff='SMOOTH', proportional_size=0.00439353)
OB.modifiers["***CUSTOM UNIQUE NAME THAT I JUST CREATED EARLIER***"].mirror_object = OA

---- ---- EDIT AFTER RESPONSE OF MARTINZ --- ---

or like this with this new "if" method that i dont know yet

import bpy 

A = bpy.context.selected_objects[0]
if "QuickMirror1" not in A.modifiers:
    bpy.ops.object.modifier_add(type='MIRROR')
    A.modifiers[len(A.modifiers)-1].name = "QuickMirror1"
    bpy.ops.object.empty_add(type='CUBE')
    bpy.ops.transform.resize(value=(0.01, 1, 1), constraint_axis=(True, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='ENABLED', proportional_edit_falloff='SMOOTH', proportional_size=0.00439353)
    E = bpy.context.selected_objects[0]
    E.name = "Mirror Axes1"
    A.modifiers["QuickMirror1"].mirror_object = E
if "QuickMirror1" in A.modifiers:
    if "QuickMirror2" not in A.modifiers:
        bpy.ops.object.modifier_add(type='MIRROR')
        A.modifiers[len(A.modifiers)-1].name = "QuickMirror2"
        bpy.ops.object.empty_add(type='CUBE')
        bpy.ops.transform.resize(value=(0.01, 1, 1), constraint_axis=(True, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='ENABLED', proportional_edit_falloff='SMOOTH', proportional_size=0.00439353)
        E = bpy.context.selected_objects[0]
        E.name = "Mirror Axes2"
        A.modifiers["QuickMirror2"].mirror_object = E
if "QuickMirror2" in A.modifiers:
    if "QuickMirror3" not in A.modifiers:
        bpy.ops.object.modifier_add(type='MIRROR')
        A.modifiers[len(A.modifiers)-1].name = "QuickMirror3"
        bpy.ops.object.empty_add(type='CUBE')
        bpy.ops.transform.resize(value=(0.01, 1, 1), constraint_axis=(True, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='ENABLED', proportional_edit_falloff='SMOOTH', proportional_size=0.00439353)
        E = bpy.context.selected_objects[0]
        E.name = "Mirror Axes3"
        A.modifiers["QuickMirror3"].mirror_object = E
if "QuickMirror3" in A.modifiers:
    if "QuickMirror4" not in A.modifiers:
        bpy.ops.object.modifier_add(type='MIRROR')
        A.modifiers[len(A.modifiers)-1].name = "QuickMirror4"
        bpy.ops.object.empty_add(type='CUBE')
        bpy.ops.transform.resize(value=(0.01, 1, 1), constraint_axis=(True, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='ENABLED', proportional_edit_falloff='SMOOTH', proportional_size=0.00439353)
        E = bpy.context.selected_objects[0]
        E.name = "Mirror Axes4"
        A.modifiers["QuickMirror4"].mirror_object = E

i got an error message

 Converting py args to operator properties:  enum "MIRROR" not found in ()

i dont understand him but my code work fine four time in a row... it seams so absurd to me that i need to do this!

there's really no way inside of python to generate a name that change each time and choose the same name inside of the code ????

thanks

Answer 1

Test Script

1. In test scripts I always use a context variable, will make cutting and pasting into Panel and Operator code easier.

2. Can add a modifier with the API (See docs Modifiers.new()). Returns a reference to the newly added mod. No need to use op and go hunting for it.

3. Use other modifiers to give a unique name eg "Mirror1", "Mirror2" on each run.

4. Use context.object .. the first member of context.selected_objects is not necessarily the active object.

 

import bpy

context = bpy.context # 
scene = context.scene
ob = context.object

nmods = sum(1 for m in ob.modifiers if m.type == 'MIRROR')
i = 0
pref = "QuickMirror"

# give it a name based on count of mods.
name = "%s%d" % (pref, i)
while ob.modifiers.get(name):    
    i += 1
    name = "%s%d" % (pref, i)

m = ob.modifiers.new(name, type='MIRROR')

bpy.ops.object.mode_set(mode='OBJECT') # required?
bpy.ops.object.empty_add(type='CUBE', view_align=False, location=(scene.cursor_location))
axis_ob = context.object
axis_ob.name = "Mirror Axes"
bpy.ops.transform.resize(value=(0.01, 1, 1), constraint_axis=(True, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='ENABLED', proportional_edit_falloff='SMOOTH', proportional_size=0.00439353)
m.mirror_object =  axis_ob

Answer 2

import bpy

C = bpy.context

if C.object is not None:
    obj = C.object # Let's work with the active object
    if "The One" not in obj.modifiers: #only create it if it's not there already
        bpy.ops.object.modifier_add(type='MIRROR')
        obj.modifiers[len(obj.modifiers)-1].name = "The One" #rename the new modifier
                                                             #that is now the last modifier
    bpy.ops.object.empty_add(type='CUBE') #The default locatioon is at cursor anyway. 
                                          #It becomes active after creation.
    obj.modifiers["The One"].mirror_object = C.object #use the active 
                                                      #object(that is the empty)
                                                      #as the mirror object
    C.object.select_set(False) #deselect the empty
    C.view_layer.objects.active = obj
    C.object.select_set(True) #Let's select the original object as it was(probably)
else:
    print("No active object")

Obviously you can also control other properties of the modifier and you could make it into an operator that you can assign to hotkeys - see the Templates menu in the header of the Text Editor.