Operation with list elements


#1

With for loop we get construction like:

take 1 element from list
     do operation A
repeat for next elements

How to achieve with pyMel this:

take 1 element from list
     do operation A
take 2 element from list
     do operation B
take 3 element from list
     do operation C
repeat for next elements

#2

You probably should read up on the basics of Python:
https://docs.python.org/2/tutorial/datastructures.html


for i in list:
  foo(i)

def foo(item):
  #do something


#3

>You probably should read up on the basics of Python:
Well, since its 100% true your answer does not helps too much :slight_smile:


#4

Something like this?


ml = [1,2,3,4,5,6,7,8,9,10, 11, 12]
for l in range(0, len(ml), 6):
	value = ml[l]
	doSomethingWithOneValue(value)
	twoValueList = ml[l+1:l+3]
	doSomethingTwoOneValue(twoValueList )
 	threeValueList =  ml[l+3:l+6]
	doSomethingTwoOneValue(threeValueList )


#5

I would have suggested either using a dictionary or a 2nd list, even though I’m unclear what you are trying to achieve.

elementList = ['e1', 'e2', 'e3']

def opA(e):
	print 'A',e

def opB(e):
	print 'B',e

def opC(e):
	print 'C',e


# either dictionary
operators = {0:opA, 1:opB, 2:opC}
for i,element in enumerate(elementList):
	operators[i](element)


# or 2nd list
operators = [opA, opB, opC]
for op, element in zip(operators, elementList):
	op(element)

David


#6

Well, i think not quite.
This code

ml = [1,2,3,4,5,6,7,8,9,10, 11, 12]
for l in range(0, len(ml), 6):
	value = ml[l]
	print 'A' + str( value)
	
	twoValueList = ml[l+1:l+3]
	print 'B' + str(twoValueList)
	
 	threeValueList =  ml[l+3:l+6]
 	print 'C' + str (threeValueList)

produce

A1
B[2, 3]
C[4, 5, 6]
A7
B[8, 9]
C[10, 11, 12]

I need to get

A [1,2,3]
B [4,5,6]
C [7,8,9]
D [10, 11, 12]


#7

Im writing script for automatic creation of object IDs for Arnold
Here what i have working — for each selected object or group i create AOV, create attribute on object, make this attribute white and feed this color to AOV.
I cant get how to build it to use 3 color instead of 1, which will reduce quantity of IDs 3 times.

import pymel.core as pm
import mtoa.aovs as aovs

# set rebder to Arnold
renderSet = pm.PyNode('defaultRenderGlobals')
renderSet.ren.set('arnold')

def checkID(*args):
    if pm.objExists('aiAOV_objectID_*'): 
        pm.select('aiAOV_objectID_*')
        exist = pm.ls(sl = True)[-1]
        exist = exist.split('_')[2]
        
        pm.select (d = True)
    else: 
        exist = 0
    return exist

def addAOV( index ): # Creates AOV render pass
    aovName = 'objectID_' + str(index)
    aovs.AOVInterface().addAOV( aovName )
    return aovName

def addColor(index): #create color attribute
    colorAttrName = 'mask_' +  str(index)
    colorAttrNameLong = 'mtoa_constant_' + str(colorAttrName)
    pm.addAttr( longName= colorAttrNameLong , niceName = colorAttrName , usedAsColor=True, attributeType='float3' )
    pm.addAttr( longName='R' +  str(colorAttrName), attributeType='float', parent=colorAttrNameLong )
    pm.addAttr( longName='G' +  str(colorAttrName), attributeType='float', parent=colorAttrNameLong )
    pm.addAttr( longName='B' +  str(colorAttrName), attributeType='float', parent=colorAttrNameLong )
    return colorAttrNameLong

def createID(index):
    # create AOV and plug aiUserDatacolor
    mskObjectMat = pm.shadingNode('aiUserDataColor', asShader=True, name = 'catchMask_' + str('%02d' % index) )
    mskObjectMat.colorAttrName.set('mask_' + str('%02d' % index))
    objectID  = addAOV ('%02d' % index)
    objectIDFull = 'aiAOV_' + str(objectID)
    ID = pm.PyNode(objectIDFull)
    mskObjectMat.outColor >> ID.defaultValue    

    
sel = pm.ls(sl = 1) #select jbject for object IDs

index = float(checkID()) + 1
for i in sel:
    createID(index)
    pm.select(i)  
    pm.runtime.SelectHierarchy()
    selShapes = pm.ls(sl = 1, shapes = True)
    pm.select(selShapes)
    msk = addColor('%02d' %index)
    
    for e in selShapes: #set mask color to white
        attr = str(e) + '.mtoa_constant_mask_' + str('%02d' % index)
        pm.setAttr(attr, [1,1,1])
           
    index += 1


#8
elementList = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]

def opA(e):
	print 'A',e

def opB(e):
	print 'B',e

def opC(e):
	print 'C',e

operators = {0:opA, 1:opB, 2:opC}
for i,element in enumerate(elementList):
	operators[i/3%3](element)

David


#9

Ok, just saw your last post…

e = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
 
 for i in xrange(0,len(e),12):
 	print 'A', e[i:i+3]
 	print 'B', e[i+3:i+6]
 	print 'C', e[i+6:i+9]
 	print 'D', e[i+9:i+12]
 

David


#10

Thanks David, looks like what i need!
Will try to implement this to my code :banghead:


#11

In my last post the method I suggested is pretty hard coded to find chunks of 3 elements, and I thought there must be something out there that is better. Sure enough Hamish McKenzie wrote a nice little generator function several years ago that is much better.

def iterBy( iterable, count ):
 	'''
 	returns an generator which will yield "chunks" of the iterable supplied of size "count".  eg:
 	for chunk in iterBy( range( 7 ), 3 ): print chunk
 
 	results in the following output:
 	[0, 1, 2]
 	[3, 4, 5]
 	[6]
 	'''
 	cur = 0
 	i = iter( iterable )
 	while True:
 		try:
 			toYield = []
 			for n in range( count ): toYield.append( i.next() )
 			yield toYield
 		except StopIteration:
 			if toYield: yield toYield
 			break
 

This makes it really easy to process a list in chunks of any size…

x = range(20)
 for i in iterBy(x,4):
 	print i
 

And we get…
[0, 1, 2, 3]
[4, 5, 6, 7]
[8, 9, 10, 11]
[12, 13, 14, 15]
[16, 17, 18, 19]

Thanks again Hamish!

David


#12

Thanks, David, the last one was easy to use.
If somebody need automatic creation of object IDs for arnold:

# 256 pipeline tools
# create object based IDs
# select objects or groups an run script
# each item in selected group will share same ID

import pymel.core as pm
import mtoa.aovs as aovs
import sys

#check if current render is Arnold
if( pm.getAttr( 'defaultRenderGlobals.currentRenderer' ) != 'arnold' ):
   pm.confirmDialog( t="Warning", message= "Set current render to Arnold!", icon='critical' )
   sys.exit( "Please use Arnold render!" )

def checkID(*args):#check existing ids to create proper nubers for next ids
    if pm.objExists('aiAOV_objectID_*'): 
        pm.select('aiAOV_objectID_*')
        exist = pm.ls(sl = True)[-1]
        exist = exist.split('_')[2]
        pm.select (d = True)
    else: 
        exist = 0
    return exist

def iterBy( iterable, count ):#Hamish McKenzie procedure to process list in blocks of N elrmrnts
 	cur = 0
 	i = iter( iterable )
 	while True:
 		try:
 			toYield = []
 			for n in range( count ): toYield.append( i.next() )
 			yield toYield
 		except StopIteration:
 			if toYield: yield toYield
 			break
 			
def addAOV( index ): # Creates AOV render pass
    aovName = 'objectID_' + str(index)
    aovs.AOVInterface().addAOV( aovName )
    return aovName

def deleteAOV(*args):# delete AOVs and aiUserDataColor shaders
    pm.delete('aiAOV_objectID_*')
    pm.delete('catchMask_*')
    
def addColor(index): #create color attribute
    colorAttrName = 'maskOBJ_' +  str(index)
    colorAttrNameLong = 'mtoa_constant_' + str(colorAttrName)
    pm.addAttr( longName= colorAttrNameLong , niceName = colorAttrName , usedAsColor=True, attributeType='float3' )
    pm.addAttr( longName='R' +  str(colorAttrName), attributeType='float', parent=colorAttrNameLong )
    pm.addAttr( longName='G' +  str(colorAttrName), attributeType='float', parent=colorAttrNameLong )
    pm.addAttr( longName='B' +  str(colorAttrName), attributeType='float', parent=colorAttrNameLong )
    return colorAttrNameLong

def createID(index):
    # create AOV and plug aiUserDatacolor
    mskObjectMat = pm.shadingNode('aiUserDataColor', asShader=True, name = 'catchMask_' + str('%02d' % index) )
    mskObjectMat.colorAttrName.set('maskOBJ_' + str('%02d' % index))
    objectID  = addAOV ('%02d' % index)
    objectIDFull = 'aiAOV_' + str(objectID)
    ID = pm.PyNode(objectIDFull)
    mskObjectMat.outColor >> ID.defaultValue    

    
sel = pm.ls(sl = 1) #select object for object IDs

index = float(checkID()) + 1
for i in iterBy(sel,3):
    #Create AOV and mask color to RED
    createID(index)
    pm.select(i[0]) 
    pm.runtime.SelectHierarchy()
    selShapes = pm.ls(sl = 1, shapes = True)
    pm.select(selShapes)
    msk = addColor('%02d' %index)
    
    for e in selShapes: #set mask color to R
        attr = str(e) + '.mtoa_constant_maskOBJ_' + str('%02d' % index)
        pm.setAttr(attr, [1,0,0])
    
    pm.select(i[1])  
    pm.runtime.SelectHierarchy()
    selShapes = pm.ls(sl = 1, shapes = True)
    pm.select(selShapes)
    msk = addColor('%02d' %index)
    
    for e in selShapes: #set mask color to G
        attr = str(e) + '.mtoa_constant_maskOBJ_' + str('%02d' % index)
        pm.setAttr(attr, [0,1,0])   
        
    pm.select(i[2])  
    pm.runtime.SelectHierarchy()
    selShapes = pm.ls(sl = 1, shapes = True)
    pm.select(selShapes)
    msk = addColor('%02d' %index)
    
    for e in selShapes: #set mask color to B
        attr = str(e) + '.mtoa_constant_maskOBJ_' + str('%02d' % index)
        pm.setAttr(attr, [0,0,1])    
    
    index += 1

And some more stuf for Arnold:
http://www.kiryha.blogspot.com/2014/02/render-notes.html


#13

Nice one. I often try to avoid selecting something in my scripts if possible. It often confuses the user if the original selection changes. To get the same result as with selectHierarchy() I use

geo = pm.listRelatives(selection, ad=True, type="mesh")

#14

Oh, yes, for me this was also weak place, thanks Haggi, will try to fix it.

Also, one more script for shader IDs:


# 256 pipeline tools
# create shader IDs for selected shading groups
# if no shading group selected AOVs created for all shading groups

import maya.cmds as cmds
import mtoa.aovs as aovs
import pymel.core as pm
import sys

#define RGB colors
R = ( 1, 0, 0 )
G = ( 0, 1, 0 )
B = ( 0, 0, 1 )

def checkShdrID(*args):#check existing ids to create proper nubers for next ids
    if pm.objExists('aiAOV_shaderID_*'): 
        pm.select('aiAOV_shaderID_*')
               
        exist = pm.ls(sl = True)[-1]
        exist = float(exist.split('_')[2]) + 1 
        
    else:
        if pm.objExists('aiAOV_*'): 
            pm.select('aiAOV_*')
            exist = pm.ls(sl = 1)
            exist = len(exist)
            
        else:
            exist = 0
    return exist
#checkShdrID()

def addObjAOV(index): # Creates AOV render pass
    aovName = 'shaderID_' + str(index)
    aovs.AOVInterface().addAOV( aovName )
    return aovName
# addObjAOV('%02d' % 0) 

def createShaderR(index):   
    shdrIDMatR = pm.shadingNode('aiUtility', asShader=True, name = 'id_R_' + str(index))
    shdrIDMatR.shadeMode.set(2)
    shdrIDMatR.color.set(R)
def createShaderG(index):   
    shdrIDMatR = pm.shadingNode('aiUtility', asShader=True, name = 'id_G_' + str(index))
    shdrIDMatR.shadeMode.set(2)
    shdrIDMatR.color.set(G)
def createShaderB(index):   
    shdrIDMatR = pm.shadingNode('aiUtility', asShader=True, name = 'id_B_' + str(index))
    shdrIDMatR.shadeMode.set(2)
    shdrIDMatR.color.set(B)
#createShaderR('%02d' % 0)

def iterBy( iterable, count ):#Hamish McKenzie procedure to process list in blocks of N elrmrnts
 	cur = 0
 	i = iter( iterable )
 	while True:
 		try:
 			toYield = []
 			for n in range( count ): toYield.append( i.next() )
 			yield toYield
 		except StopIteration:
 			if toYield: yield toYield
 			break
    
# check if any Shading Group selected or not
shdrs = pm.ls(sl = 1)
if shdrs:
    print 'Shading groups selected manualy'
else:
    confirm = pm.confirmDialog ( title='WARNING', message='No shading group selected, create IDs for all shades in scene?', button=['Yes','No'], defaultButton='Yes', cancelButton='No', dismissString='No' )
    if confirm == 'Yes':
        shdrs = pm.ls(type='shadingEngine')
        shdrs.remove('initialParticleSE')
        shdrs.remove('initialShadingGroup')
    else:
        sys.exit()

print shdrs    
   
index =  checkShdrID()   
for i in iterBy(shdrs,3):
    addObjAOV('%02d' %index) #create AOV
    
    #create and plug R
    createShaderR('%02d' %index)
    shader = 'id_R_%02d' %index
    SHD = pm.PyNode(shader)
    SHD.outColor >> i[0].aiCustomAOVs[index].aovInput;
    #create and plug G
    if i[1]:
        createShaderG('%02d' %index)
        shader = 'id_G_%02d' %index
        SHD = pm.PyNode(shader)
        SHD.outColor >> i[1].aiCustomAOVs[index].aovInput;
    
    #create and plug B
    if i[2]:
        createShaderB('%02d' %index)
        shader = 'id_B_%02d' %index
        SHD = pm.PyNode(shader)
        SHD.outColor >> i[2].aiCustomAOVs[index].aovInput;    
    
    index +=1
    


#15

Well, not a big surprize that shader ID script works only in ideal conditions.
In general script create Red, Green, Blue shaders, AOVs and connect shader to AOVs input attributes.

This is part, where connection is done:

SHD.outColor >> i[0].aiCustomAOVs[index].aovInput;

Result: id_R_00.outColor aiStandard1SG.aiCustomAOVs[0].aovInput;

This index in aiCustomAOVs[index] is serial number of created AOV.
So, if we create some AOV in scene before running script, the index of first AOV is not 0 and connections mess up. I`m doing check of existing AOVs and correct index according to this, but anyway sooner or later after several script execution and AOV operation index will mess.

Im stuck. May be somebody has solved same issue with this?


#16

Well… list comprehensions is also way to go?

nums = [1,2,3]
fruit = ["Apples", "Peaches", "Pears", "Bananas"]
print [(i,f) for i in nums for f in fruit]

[(1, ‘Apples’), (1, ‘Peaches’), (1, ‘Pears’), (1, ‘Bananas’),
(2, ‘Apples’), (2, ‘Peaches’), (2, ‘Pears’), (2, ‘Bananas’),
(3, ‘Apples’), (3, ‘Peaches’), (3, ‘Pears’), (3, ‘Bananas’)]