For loop randomly stopping and not working

Im writing a program to grab all of the md5sums of a certain file but it stops around 40000 any help would be great, here is my program. NOTE: 40000 has no meaning other than it just breaks there

def grabmd5():
    for x in range(0, numLinesofFile):
            f = open(finfile1, 'r')
            for line in f:
            line = line.strip('\n')
            os.system("md5sum " + line + " 2>/dev/null" + " >> file2.txt")
    if x == size:
        break
        print("all done")
    else:
        continue