How to randomly select an item from a list?
Assume I have the following list:
foo = ['a', 'b', 'c', 'd', 'e']
What is the simplest way to retrieve an item at random from this list?
Use random.choice :
import random
foo = ['a', 'b', 'c', 'd', 'e']
print(random.choice(foo))
For cryptographically secure random choices (eg for generating a passphrase from a wordlist), use random.SystemRandom class:
import random
foo = ['battery', 'correct', 'horse', 'staple']
secure_random = random.SystemRandom()
print(secure_random.choice(foo))
如果你还需要索引：
foo = ['a', 'b', 'c', 'd', 'e']
from random import randrange
random_index = randrange(0,len(foo))
print foo[random_index]
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 = 2 # 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]
second_random_item = list_of_random_items[1]
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.
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