CODEWITHSUNDEEP
pythonlistrandom
Materials
Materials

Reputation: 149

How do I pick x random elements from a list, for x > len(list)?

I need to pick random elements from a list. And the number of random elements is larger than the length of the list (so I will have duplicates). Therefore I can't use random.sample(), because the sample can't be larger than the population. Does anyone have a solution?

For example:

lst = [1,2,3,4]

How can I pick 5 random elements from this list, like [1,4,3,1,2]?

Upvotes: 0

Views: 935

Answers (5)

clement
clement

Reputation: 21

My answer involves the random.choice function and a list comprehension.

I suggest also to put the magic inside a function whose name makes explicit what it does.

import random

def pick_n_samples_from_list(n, l):
    return [random.choice(l) for n in range(n)]

n = 5
lst = [1, 2, 3, 4]
print(pick_n_samples_from_list(n, lst))
>[3, 1, 4, 4, 1]

Upvotes: 0

zondo
zondo

Reputation: 20336

You need no third-party modules. Just use a list comprehension:

choices = [random.choice(lst) for _ in range(5)]

Another way that is a little shorter, but not as efficient is this:

choices = list(map(random.choice, [lst]*5))

In Python2, map() already returns a list, so you could do:

choices = map(random.choice, [lst]*5)

Upvotes: 0

PM 2Ring
PM 2Ring

Reputation: 55469

Use random.choice in a loop or list comprehension to return random elements from your input list.

Here's a list comprehension example:

from random import choice

lst =  [10, 20, 30, 40]

num = 5
seq = [choice(lst) for _ in range(num)]
print(seq)

typical output

[20, 40, 10, 30, 20]

And here's the same thing using a "traditional for loop:

from random import choice

lst =  [10, 20, 30, 40]

num = 5
seq = []
for _ in range(num):
    seq.append(choice(lst))
print(seq)

Upvotes: 0

Linus Thiel
Linus Thiel

Reputation: 39223

If I understand correctly, that you want to pick at random from a population, this should do the trick:

import random

list = [1, 2, 3, 4]

random_elements = [random.choice(list) for n in range(5)]

Upvotes: 2

Alan
Alan

Reputation: 9610

import numpy
lst = [1,2,3,4]
choices = numpy.random.choice(lst, size=5, replace=True)

Upvotes: 0

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