tx andreas, an exciting world

i got a bit further with my findSlot(Mat, some_shader) 
and dont understand why i get Attribute Errors when i iterate over a bc:

def findSlot_v1(sh) : # sh = some shader already inserted in a material slot
bc = mat.GetDataInstance()
for i, v in bc:
print i, v
if v == sh: return i

--> AttributeError: Parameter value not accessible (object unknown in Python)

def findSlot_v2(sh) : # sh = some shader already inserted in a material slot
bc = mat.GetDataInstance()
for i, v in bc:
try:
if v == sh: return i
except AttributeError:
pass

--> AttributeError: Parameter value not accessible (object unknown in Python)

def findSlot_v3(sh) : # sh = some shader already inserted in a material slot
bc = mat.GetDataInstance()
for i in range(len(bc) - 1) :
try:
index = bc.GetIndexId(i)
if op[index] == sh: return index
except AttributeError:
pass

--> this finally works

but could anybody tell me why i get these strange AttributeErrors ?

the first version is straight from the book:
https://developers.maxon.net/docs/py/2023_2/modules/c4d/BaseContainer/index.html?highlight=basecontainer#BaseContainer.\__iter\_\_

and... i guess there no nicer/faster solution without iterating over the complete bc?

best, index

Hi index,

welcome to the Plugin Café forums 

Unfortunately no, there is no such function. If the shader setup is simple enough, you could just have an array with parameter IDs and then compare the linked shaders in your own FindSlot() function. A bit more complicated it gets, if the shader setups can be more complicated, including sub-shaders, like e.g. layer shader. Then you have to additionally iterate the shader tree for each slot.