Selective averaging in python

so this code just randomises the list 1,2,3,4(x4) then writes it out into text file and reads it back out. It prints all the 16, however i was wondering if there was a way make 4 groups of 4 out of the 16, then I could define it and call them individually and take an average of only 4 of them.

import random
members = 5
participants=[1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4]
random.shuffle(participants)
with open("myfile1.txt",'w') as tf:
    for i in range(len(participants) // members + 1):
        group = participants[i*members:i*members + members]
        for participant in group:
            tf.write(str(participant))
            tf.write("\n")

with open("myfile1.txt",'r') as tf:
    for line in tf.readlines():
        print(line)

def ing():
    with open('myfile1.txt','r') as file:
        print(sum(list(map(int,[elem for elem in file.read().split('\n') if elem!='']))))

Sorry its a bit waffly, basically want to take an average of the first 4 numbers it spits out!

Thanks!