ValueError: I/O operation - python-2.7

Question

I see following error when executing this python code. What is issue here?
I have used "sys.stdout.close()" still I see these errors.
#! /usr/bin/python
import sys
a = [ 10, 12, 13, 14]
sys.stdout=open("file.txt","w")
print("++++++++")
print("***xyz***")
print("++++++++")
sys.stdout.close()
for i in a:
print i
Output:
Traceback (most recent call last):
File "./test3.py", line 10, in <module>
print i
ValueError: I/O operation on closed file`

Answer 1

You are trying to write to stdout (your file) after closing it. At line 8 you close the file, and at line 10 you call print.
If you want to write the list a to the file you should close it after the for loop.

Answer 2

Consider using with open because you don't have to worry about closing it. If your list needs to be a list then consider pickling it instead of writing it to a file. Pickling serializes your data.
#!python3
# import module
from os import system
import pickle
# clear the screan
system('cls')
a = [ 10, 12, 13, 14]
# write a list to file, but it has to be written as a string
with open('file.txt', 'w') as wf:
wf.write(str(a))
# when you open your file up, the data is a string
with open('file.txt', 'r') as fp:
for item in fp:
print(item)
print(type(item))
# if you want to retain your data as a list, then pickle it
output = open('file.pkl', 'wb')
pickle.dump(a, output)
output.close()
# open up a pickled file
pkl_file = open('file.pkl', 'rb')
data = pickle.load(pkl_file)
print(data)
print(type(data))
pkl_file.close()