How to randomly select an item from a list?

Question

Assume I have the following list:

foo = [\'a\', \'b\', \'c\', \'d\', \'e\']

What is the simplest way to retrieve an item at random from thi

Answer 1

The following code demonstrates if you need to produce the same items. You can also specify how many samples you want to extract.
The sample method returns a new list containing elements from the population while leaving the original population unchanged. The resulting list is in selection order so that all sub-slices will also be valid random samples.

import random as random
random.seed(0)  # don't use seed function, if you want different results in each run
print(random.sample(foo,3))  # 3 is the number of sample you want to retrieve

Output:['d', 'e', 'a']

Answer 2

numpy solution: numpy.random.choice

For this question, it works the same as the accepted answer (import random; random.choice()), but I added it because the programmer may have imported numpy already (like me) & also there are some differences between the two methods that may concern your actual use case.

import numpy as np    
np.random.choice(foo) # randomly selects a single item

For reproducibility, you can do:

np.random.seed(123)
np.random.choice(foo) # first call will always return 'c'

For samples of one or more items, returned as an array, pass the size argument:

np.random.choice(foo, 5)          # sample with replacement (default)
np.random.choice(foo, 5, False)   # sample without replacement

Answer 3

This is the code with a variable that defines the random index:

import random

foo = ['a', 'b', 'c', 'd', 'e']
randomindex = random.randint(0,len(foo)-1) 
print (foo[randomindex])
## print (randomindex)

This is the code without the variable:

import random

foo = ['a', 'b', 'c', 'd', 'e']
print (foo[random.randint(0,len(foo)-1)])

And this is the code in the shortest and smartest way to do it:

import random

foo = ['a', 'b', 'c', 'd', 'e']
print(random.choice(foo))

(python 2.7)

Answer 4

I propose a script for removing randomly picked up items off a list until it is empty:

Maintain a set and remove randomly picked up element (with choice) until list is empty.

s=set(range(1,6))
import random

while len(s)>0:
  s.remove(random.choice(list(s)))
  print(s)

Three runs give three different answers:

>>> 
set([1, 3, 4, 5])
set([3, 4, 5])
set([3, 4])
set([4])
set([])
>>> 
set([1, 2, 3, 5])
set([2, 3, 5])
set([2, 3])
set([2])
set([])

>>> 
set([1, 2, 3, 5])
set([1, 2, 3])
set([1, 2])
set([1])
set([])

Answer 5

We can also do this using randint.

from random import randint
l= ['a','b','c']

def get_rand_element(l):
    if l:
        return l[randint(0,len(l)-1)]
    else:
        return None

get_rand_element(l)

Answer 6

Use random.choice()

import random

foo = ['a', 'b', 'c', 'd', 'e']
print(random.choice(foo))

For cryptographically secure random choices (e.g. for generating a passphrase from a wordlist) use secrets.choice()

import secrets

foo = ['battery', 'correct', 'horse', 'staple']
print(secrets.choice(foo))

secrets is new in Python 3.6, on older versions of Python you can use the random.SystemRandom class:

import random

secure_random = random.SystemRandom()
print(secure_random.choice(foo))