python - Value Error : invalid literal for int() with base 10: '' -

i'm new in python , don't know why i'm getting error sometimes.

this code:

import random sorteio = [] urna = open("urna.txt")  y = 1 while y <= 50:     sort = int(random.random() * 392)     print sort     while sort > 0:         x = urna.readline()         sort = sort - 1     print x       sorteio = sorteio + [int(x)]     y = y + 1 print sorteio 

where urna.txt file on format:

1156 459 277 166 638 885 482 879 33 559 

i'll grateful if knows why error appears , how fix it.

upon attempting read past end of file, you're getting empty string '' cannot converted int.

>>> int('') traceback (most recent call last):   file "<stdin>", line 1, in <module> valueerror: invalid literal int() base 10: '' 

to satisfy requirement of selecting 50 random lines text value, if understand problem correctly:

import random  open("urna.txt") urna:     sorteio = [int(line) line in urna] # lines of file ints  selection = random.sample(sorteio, 50)  print selection