Random sample of paired lists in Python

Question

I have two lists x and y, both of length n, with x_i and y_i forming a pair. How could I take a random sample of m values from these two lists while preserving the pairing information (e.g. x[10] and y[10] would be together in the resulting sample)

My initial idea is this.

• use zip to create a list of tuples
• shuffle the list of tuples
• select the first m tuples from the list
• break up the tuples into new paired lists

And the code would look something like this.

templist = list()
for tup in zip(x, y):
    templist.append(tup)
random.shuffle(templist)
x_sub = [a for a, b in templist[0:m]]
y_sub = [b for a, b in templist[0:m]]

This seems rather kludgy to me. Is there any way I could make this more clear, concise, or Pythonic?

Answer 1

You can sample m pairs and split those into two lists with the following code:

import random

x = list(range(1, 10))
y = list("abcdefghij")
m = 3

x_sub, y_sub = zip(*random.sample(list(zip(x, y)), m))