Question

I have a program that uses curses, and then returns to the main script for further processing. After it returns, my subsequent output to stdout does not appear until there’s a large amount of it (e.g. thousands of bytes).

I’ve reduced the problem to a very simple program that fails reliably:

import curses
import time

curses.initscr()
curses.endwin()

print "Hello world!"
time.sleep(5)

If I comment out the two curses calls, the ‘Hello world!’ prints before the delay. If I put them in, it prints after the delay (when the script exits).

Answer 1

The curses.endwin() call “sets standard I/O back to normal”… which unfortunately means “buffered” (you could consider that a bug in curses and file the bug on Python’s tracker).

To ensure standard-output is unbuffered,

import os

sys.stdout = os.fdopen(0, 'w', 0)

(You can put the import os at the start, or course; the reassignment of sys.stdout is meant to go right after the endwin call).