The random.sample() function in Python is part of the built-in random module and is used to generate a random sample from a specified population. Unlike random.choice(), which selects a single random element, random.sample() allows you to select multiple unique elements from a sequence without replacement. This means that the same element cannot be selected more than once in a single call.

Syntax

import random
sample = random.sample(population, k)

• Parameters:
  • population: A sequence (like a list, tuple, or string) from which to sample.
  • k: The number of unique elements to select from the population. Must be less than or equal to the size of the population.

Return Value

• Returns a list of k unique elements chosen from the population.

Example Usage

1. Basic Example:

   import random
   
   population = [1, 2, 3, 4, 5]
   sample = random.sample(population, 3)  # Select 3 unique elements
   print(sample)  # Example output: [2, 5, 1]
   

2. Sampling from a List of Strings:

   fruits = ['apple', 'banana', 'cherry', 'date', 'fig']
   sample = random.sample(fruits, 2)  # Select 2 unique fruits
   print(sample)  # Example output: ['banana', 'fig']
   

3. Sampling with a Larger Population:

   population = range(1, 101)  # Population of numbers from 1 to 100
   sample = random.sample(population, 5)  # Select 5 unique numbers
   print(sample)  # Example output: [24, 78, 3, 56, 19]
   

4. Attempting to Sample More Than Available: If you try to sample more elements than are available in the population, a ValueError will be raised:

   try:
       sample = random.sample(fruits, 10)  # This will raise an error
   except ValueError as e:
       print(e)  # Output: Sample larger than population or is negative
   

5. Seeding the Random Number Generator: You can use random.seed() to ensure reproducibility:

   random.seed(42)  # Seed the random number generator
   sample = random.sample(population, 3)
   print(sample)  # Output will be the same each time the seed is set
   

Summary

• random.sample(population, k) is a versatile function for selecting multiple unique elements from a given sequence.
• It is useful in various applications, such as random sampling, simulations, and games.
• The function raises a ValueError if k is larger than the size of the population, so it's important to ensure that you specify a valid sample size.