import os

def test(file):
    # hna ghadi ikoun test
    return "{}!@#$$".format(file)

path = "."
for  root, dirs, files in os.walk(path):
    first = 0
    last = 3
    for i in range(0,len(files),3):
        te = list(map(test,files[i:i+3]))
        print(te)