[FIXED] Python divide list into percentages

Issue

I have a function that applies random colors to each set of elements defined by a percentage. In this case I have a list of 154 elements to start with, but somehow in the end I get only 152 processed elements. Not sure why, because I am giving it 100% in total when I call the function at the end.

import maya.cmds as cmds
import random

def selector(percents):
    RandomSelection = []
    mySel = cmds.ls(sl=1) # a list of elements with a total of 154
    random.shuffle(mySel)
    
    start = 0
    for cur in percents:
        end = start + cur * len(mySel) // 100
        RandomSelection.append(mySel[start:end])
        start = end
    
    print(len(mySel)) # 154
    print ( sum( [ len(listElem) for listElem in RandomSelection]) ) # 152 # why not 154?
    
    for mesh in RandomSelection:
        r = [random.random() for i in range(3)]
        cmds.polyColorPerVertex(mesh,rgb=(r[0], r[1], r[2]), cdo=1 )
    

selector([70, 10, 15, 5])
#154
#152

Thank you.

Solution

end = start + cur * len(mySel) // 100 can drop up to 1 element at each iteration due to flooring.

Try this instead :

start = 0
cumul = 0
for cur in percents:
    cumul += cur
    end = cumul * len(mySel) // 100
    RandomSelection.append(mySel[start:end])
    start = end

This will still drop up to 1 at every iteration due to florring, but these drops won't accumulate (since you recompute your end from fresh), and at the end you are guaranteed to have an exact division, and so use up all elements.

Answered By - Julien