import random

def my_func(a, b, n, file):
    spis = [random.uniform(a,b) for _ in range(n)] 
    fp = open(file=file, mode='w')
    for i in range(round(len(spis)/3)+1):
        fp.write(str(spis[i*3:(i+1)*3])+'\n')
    fp.close()
    return spis