Creating a list of colors based upon a partition of the set {0,1,..,n-1}-CodePudding

I have a partition of the set {0,1,...,n-1} into a list of m subsets along corresponding to m colors. I need to assign each index in my set to the corresponding color.

As a simple example, if n=8 and m=3, let

partition=[{0,2},{1,4,6},{3,5,7}]
colors=['r','b','c']

I want to create the list ['r','b','r','c','b','c','b','c']

What is the most "pythonic" way of doing this, preferably without loops?

CodePudding user response：

One way is to create a mapping from partition to colors, sort it; then get the values:

d = {k:v for s, v in zip(partition, colors) for k in s}
out = [d[k] for k in sorted(d)]

Output:

['r', 'b', 'r', 'c', 'b', 'c', 'b', 'c']

CodePudding user response：

I would personally go for this approach (it does involve for loops, but uses zip which is quite Pythonic):

n = 8

partitions = [{0,2},{1,4,6},{3,5,7}]
colors = ['r','b','c']

result = [''] * n # or result = [None] * n
for color, partition in zip(colors, partitions):
    for index in partition:
        result[index] = color
    
print(result) # prints ['r', 'b', 'r', 'c', 'b', 'c', 'b', 'c']