Select Random Element from Set in Python

In this article, we will see how to select a random element from a set in Python.
We have the random module in Python which implements pseudo-random number generators for various distributions including integer, float.
Also, we will see to randomly select multiple choices from a set.

Random number operations in set in Python

random.choice()

This function retrieves a single element from the set.

# program using choice() function

import random
set = (11, 22, 33, 44, 55, 66, 77, 88) 

print("A random number from the set is: " , random.choice(set))

Output:

A random number from the set is: 77

random.choices()

As we know random.choice() is used for selecting single element whereas random.choices()  is used to select multiple elements specified in its argument.  This function takes 2 arguments, set_name  and k(number of random items)

import random

movie_list = ('Godfather', 'Modern Times', 'Casablanca', 'Metropolis', 'Mary Poppins', 'Spartacus')
item = random.choices(movie_list, k=2)

print("Randomly selected items from movie_list are: ", item)

Output:

Randomly selected items from movie_list are:  ['Spartacus', 'Godfather']

 

random.sample()

Likewise, random.sample() can be used instead  random.choices(). Both arguments and output for random.sample() are similar to random.chocies().

import random

movie_list = ('Godfather', 'Modern Times', 'Casablanca', 'Metropolis', 'Mary Poppins', 'Spartacus')
item = random.sample(movie_list, k=2)

print("Randomly selected items from movie_list are: ", item)

Output:

Randomly selected items from movie_list are:  ['Metropolis', 'Casablanca']

randrange()

Furthermore, many times we need an item from a set along with its index position. We can accomplish it by making use of randrange() function. So let us now see how randomly chose an item along with its index number.

from random import randrange

movie_list = ('Godfather', 'Modern Times', 'Casablanca', 'Metropolis', 'Mary Poppins', 'Spartacus')
random_index = randrange(len(movie_list))
movie_item = movie_list[random_index]
print ("Randomly selected item and its index is - ", movie_item, "\nIndex - ", random_index)

Output:

Randomly selected item and its index is -  Casablanca 
Index -  2

Also read,

• Create union of sets
• select second greatest number in a set

4 responses to “Select Random Element from Set in Python”

1. Tom says:

   April 7, 2020 at 3:43 pm

   Hi Prakhar,
   I think there is an important matter i your code.
   You shouldn’t ever use the Python built-in classname ‘set’ as a variable name.
   The variable which is defined here as
   set = (11, 22, 33, 44, 55, 66, 77, 88)
   is actually a tuple.
   Perhaps use
   number_options = (11, 22, 33, 44, 55, 66, 77, 88)
   or
   number_set = set((11, 22, 33, 44, 55, 66, 77, 88))
   instead.

   Additionally, it is confusing to call a variable movie_list, when it is a tuple, not a Python list.
   Either use
   movie_list = [‘Godfather’, ‘Modern Times’, ‘Casablanca’, ‘Metropolis’, ‘Mary Poppins’, ‘Spartacus’]
   or just
   movies = (‘Godfather’, ‘Modern Times’, ‘Casablanca’, ‘Metropolis’, ‘Mary Poppins’, ‘Spartacus’)

   Reply
2. Dan says:

   June 23, 2020 at 10:08 am

   thanks for the article.

   however, random.choice() works on lists, not sets. your ‘set’ is actually a list! to make a set you would need to use curly braces ie
   set = {11, 22, 33, 44, 55, 66, 77, 88}
   if you change this in your code you will see an error “‘set’ object is not subscriptable”

   Reply
3. Sebastian Gonzalez Tirado says:

   October 14, 2020 at 3:13 pm

   In addition to the comments from Tom and Dan, you would need to use random.sample() in order to retrieve a random element from a set:

   set_example = set(11, 22, 33, 44, 55, 66, 77, 88)
   random.sample(set_example, 1) # For 1 element of the set

   Reply
4. Vandana says:

   December 28, 2021 at 8:47 pm

   L= [{1,2,3,4},{2,3,5}]
   Now how to count number 3 in this list of sets

   Reply