python seek and write

gistfile1.txt

import random
print("opening file")
maxlines = 50
file = open("test.txt","a+")
file.seek(0,0)
ind_str = file.readline()
indicator = int(ind_str)
file.seek(len(ind_str)+indicator)
line = "%6d\n" % (random.randint(0,0xFFFF))
file.seek(0,0)
line = "%6d\n" % (indicator+len(ind_str)+8)
file.write(line)
print("closing file")
file.close()