Looping over hierarchies of objects with Python

Question

Today I'm able to select all parameters that I need. But select a object it's pretty simple, using name it's ok.

But I use a very complex hierarchy in blender. As you can see just below:

Thereby I start with a simpler example and try to created a script just to print each object with their name and save the hierarchy, but some difficulties appears to me.

First I start to use type and be sure to conserve the hierarchy.

I decide to use an Empty as a "structure node".

So if I come across a Mesh I just print its name and if it's "EMPTY" I print its name. After printing all the mesh's names I check to see if another Empty is in the same block. I then go to the next one and do the same things. I do this for the entire group, it's a recursive function I think.

This is my Outliner:

But I have two difficulties:

First, I try this script to print the object, but didn't work well. I'm a newbi sorry if there is mistake. Could you help me to understand why it doesn't work?

Secondly, I tried something simpler, just to print by type, starting from the first one to the second one, but it seems to print by alphabetical order. I don't know what happened.

I've tried so many things in a week and now I'm here for your help. Could you take the time to help?

I am at your disposal for further information.

EDIT 25/07/2019

Hello evvery one,

So i try myself to find a solution, and it's pretty hard for me .

I created two function to created a list with all original parents

def explo_hie(id_scene): 
    global memoire_1
    global generation_1
    memoire_1=[]
    generation_1=[]
    for o in bpy.data.scenes[id_scene].objects:
        memoire_1.append(o.name) 
    ##
    k = len(memoire_1)
    ##
    for i in range(0,k) :
        if bpy.data.objects[memoire_1[i]].parent == None :
            generation_1.append(memoire_1[i])
            print("Add")
        else :
            print("Do nothing because has parent")
    ##
    print("First genration or origal parents",generation_1)
    ##
    w = len(generation_1)
    ##   
    for a in range (0,w):
        memoire_1.remove(generation_1[a])       
    ##
    print(memoire_1)

explo_hie("Scene")

And it's work pretty weel i'm pround of me, but i think there is some upgrades to do.

But my probleme is over the looping, because as you can see i created a code to check types of objects :

################       
#Step One 
################

# We need to knwo the len of the generation_1
#This list contains the first object of our generation
k = len(generation_1) 

#I scan all object of this list
#For each index i check the type           
for i in range(0,k) :
    type = bpy.data.objects[generation_1[i]].type
    if type == 'MESH': 
        print("Func grab mesh",type)
    elif type == 'EMPTY':
        print("It's a structural node",type)
    else :
        print("User you don't respect rules",type))

But as you can see it's note a reccursive fonction so i tried to do this :

################       
#Step Two 
################

# We need to knwo the len of the generation_1
#This list contains the first object of our generation
k = len(generation_1) 

#I scan all object of this list
#For each index i check the type           
for i in range(0,k) :
    type = bpy.data.objects[generation_1[i]].type
    if type == 'MESH': 
        print("Func grab mesh")
    elif type == 'EMPTY':
        print("It's a structural node",type)
        #But if it's a structural noed i need to check if it has children 
        nbr_enfants = bpy.data.objects[generation_1[i]].children
        if len(nbr_enfants) == 0 :
            print("Pas d'enfants fonction get info")
        else :
            print(nbr_enfants)
            a=len(nbr_enfants)
            for o in range(0,a) :
                e = nbr_enfants[o]
                print()
                type = bpy.data.objects[e].type
                if type == 'MESH': 
                    print("Fonction grab mesh")
                elif type == 'EMPTY':
                    print("reccursive func")
                else :
                    print("User you don't respect rules",type)         
    else :
        print("User you don't respect rules",type))

But i'm not able to created a the reccursive function ... and to be honnest i don't really understand how to do it. I try some simple exemple for algebric operation and i achiv it but for blender i don't know how to do it. Could you help me ?

Answer 1

Printing the hierarchy

Note sure if this totally answers your question, but it shows how to traverse a hierarchy recursively. Code similar from

How do I copy children of an object using copy() method, without messing up their positions?

and Show and Hide child objects along with Parent

Test script to recursively run thru the hierarchy. Change the levels keyword argument to go deeper than 10.

import bpy
scene = bpy.context.scene

def print_heir(ob, levels=10):
    def recurse(ob, parent, depth):
        if depth > levels: 
            return
        print("  " * depth, ob.name)

        for child in ob.children:
            recurse(child, ob,  depth + 1)
    recurse(ob, ob.parent, 0)

root_obs = (o for o in scene.objects if not o.parent)

for o in root_obs:
    print_heir(o)

 Lamp
 Camera
   Cube.003
     Cube
       Cube.001
       Cube.005
 Cube.002
 Cube.004