import glob

sciezka = "/scores/model.iter*.npz.bleu"

for file in glob.glob(sciezka):
    with open(file, 'r') as plik:
        for line in plik.readlines():
            bleu = float(line[line.find("=")+ 1:line.find(",")])
            if bleu >0:
                max = bleu
                maxi = file

            plik.close()

print ( maxi )