Python: create adaptives Suffix i want to know how to create adaptive suffix, that are "content aware" of the situation,  to avoid erasing object that have the same names. i think that this is a classic use of python, could someone explain or give me a link to a explanation/ tutorial that can help me understand how this adaptive renaming system work ?

for example in this code below im automatically creating a save as copy in the directory file. 

import bpy
import os

try:
    os.mkdir(os.path.dirname(bpy.data.filepath)+"\\save as copy\\")
except: 
    print('directory already created')

Dir = os.path.dirname(bpy.data.filepath) + "\\save as copy\\"

bpy.ops.wm.save_as_mainfile(copy=True, filepath= Dir +"Copy.blend")


the only problem is that it erase the previous .blend everytime i do the action, id much prefer to implement an adaptive suffix, that create "copy 001" if copy already exist; "copy 002" if 001 already exist... i could do that with condition but i dont know how to reproduce the steps indefinitely. 

in a precedent code someone show me a way to do this ? i dont know if its specific to the situation or not, but i didnt understand how to reproduce thoses act for my situation:

import bpy

context = bpy.context
scene = context.scene
A = context.object

i = 1
pref = "%s Mirror " % A.name

name = "%s%d" % (pref, i)
while A.modifiers.get(name):    
    i += 1
    name = "%s%d" % (pref, i)


bpy.ops.object.modifier_add(type='MIRROR')
A.modifiers[len(A.modifiers)-1].name = name
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 = name
A.modifiers[name].mirror_object = E
A.select_set(state=True)


i tried 

import bpy

i = 1
pref = "neww"
name = "%s%d" % (pref, i)
while bpy.context.object.name.get(name): 
    i += 1
    name = "%s%d" % (pref, i)

for ob in bpy.context.selected_objects:
    ob.name = name


i also tried 

import bpy

i = 1
pref = "new"
name = "%s%d" % (pref, i)

while ob.name = name
    i += 1
    name = "%s%d" % (pref, i)

for ob in bpy.context.selected_objects:
    ob.name = name


dont work
found it 

import bpy

i = 0 #default number
pref = "new" #name
name = "%s%d" % (pref, i)

for ob in bpy.context.selected_objects: #for every object in selection
    i += 1 #add i+1
    name = "%s%d" % (pref, i) #redefinie name
    ob.name = name


if i wanted to just keep the same name, i need to replace pref by 

pref = "%s" % bpy.context.object.name


if i want to make the prefix into a suffix or add _ - ect i just need to change 

name = "%s%d" % (pref, i)
to
name = "%s_%d" % (pref, i)


basically its simple, for each object in my selection, i add +1 to i = 1
that's it 

there is also a special python function that transform the number into numbers like 001 002 003 010.. ect... ii only work with strings so you need to convert the number into a string first:

newnumberfilledwithzeros =str(10).zfill(3) #will be = to 010


with all thoses examples, here what i came with this example below,
and witouth the " "%s" method, its actually not necessary for this small exercise.

name="hello"
#if you want to keep the same name and just add the suffix ? use this line below instead
#name= bpy.context.selected_object.name
start=0 #could start at -1 if you want the first obj to be named 000
zeros=3 #3x= numbers like 001,019... 4x = 0012,0003... ...
for ob in bpy.context.selected_objects:
    start+=1
    f=str(start).zfill(zeros)
    ob.name = name + f
    #result will be "hello001" "hello002" "hello003" ect..
    #want to be "hello_001" ? just to this below 
    #ob.name = name + "_" + f
    #want to do a prefix ? 
    #ob.name = f + "_" + name