How do I randomly select an item from a list using Python?

Let's say, as an example, I have the following list:

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

What is the best way to retrieve an item at random from this list?

Answers


import random

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

In case you also need the index:

foo = ['a', 'b', 'c', 'd', 'e']
from random import randrange
random_index = randrange(0,len(foo))
print foo[random_index]

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([])

import random
random_item = random.choice(foo)

Bit more pythonic way of doing it


If you want to randomly select more than one item from a list, or select an item from a set, I'd recommend using random.sample instead.

import random
group_of_items = {1, 2, 3, 4}               # a sequence or set will work here.
num_to_select = 1                           # set the number to select here.
list_of_random_items = random.sample(group_of_items, num_to_select)
first_random_item = list_of_random_items[0]

If you're only pulling a single item from a list though, choice is less clunky, as using sample would have the syntax random.sample(some_list, 1)[0] instead of random.choice(some_list).

Unfortunately though, choice only works for a single output from sequences (such as lists or tuples). Though random.choice(tuple(some_set)) may be an option for getting a single item from a set.


if you need the index just use:

import random
foo = ['a', 'b', 'c', 'd', 'e']
print int(random.random() * len(foo))
print foo[int(random.random() * len(foo))]

random.choice does the same:)


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

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)


import random
print list[random.randint(0, len(list)-1)]

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