[python] Select 50 items from list at random to write to file

So far I have figured out how to import the file, create new files, and randomize the list.

I'm having trouble selecting only 50 items from the list randomly to write to a file?

def randomizer(input,output1='random_1.txt',output2='random_2.txt',output3='random_3.txt',output4='random_total.txt'):

#Input file 
    query=open(input,'r').read().split()
    dir,file=os.path.split(input)

    temp1 = os.path.join(dir,output1)
    temp2 = os.path.join(dir,output2)
    temp3 = os.path.join(dir,output3)
    temp4 = os.path.join(dir,output4)


    out_file4=open(temp4,'w')

    random.shuffle(query)

    for item in query:
        out_file4.write(item+'\n')   

So if the total randomization file was

example:

random_total = ['9','2','3','1','5','6','8','7','0','4']

I would want 3 files (out_file1|2|3) with the first random set of 3, second random set of 3, and third random set of 3 (for this example, but the one I want to create should have 50)

random_1 = ['9','2','3']
random_2 = ['1','5','6']
random_3 = ['8','7','0']

So the last '4' will not be included which is fine.

How can I select 50 from the list that I randomized ?

Even better, how could I select 50 at random from the original list ?

Say your list has 100 elements and you want to pick 50 of them in a random way. Here are the steps to follow:

1. Import the libraries
2. Create the seed for random number generator, I have put it at 2
3. Prepare a list of numbers from which to pick up in a random way
4. Make the random choices from the numbers list

Code:

from random import seed
from random import choice

seed(2)
numbers = [i for i in range(100)]

print(numbers)

for _ in range(50):
    selection = choice(numbers)
    print(selection)

I think random.choice() is a better option.

import numpy as np

mylist = [13,23,14,52,6,23]

np.random.choice(mylist, 3, replace=False)

the function returns an array of 3 randomly chosen values from the list

One easy way to select random items is to shuffle then slice.

import random
a = [1,2,3,4,5,6,7,8,9]
random.shuffle(a)
print a[:4] # prints 4 random variables