Amjith Amjith - 3 months ago 26
Python Question

How to flush the input stream in python?

I'm writing a simple alarm utility in Python.

#!/usr/bin/python

import time
import subprocess
import sys

alarm1 = int(raw_input("How many minutes (alarm1)? "))

while (1):
time.sleep(60*alarm1)
print "Alarm1"
sys.stdout.flush()
doit = raw_input("Continue (Y/N)?[Y]: ")
print "Input",doit
if doit == 'N' or doit=='n':
print "Exiting....."
break


I want to flush or discard all the key strokes that were entered while the script was sleeping and only accept the key strokes after the raw_input() is executed.

EDIT: I'm running this on windows xp.

Answer

It would help to know what operating system you're using, as this is a very operating-system-specific question. For example, Kylar's answer doesn't work on Windows because sys.stdin doesn't have a fileno attribute.

I was curious and threw together a solution using curses, but this won't work on Windows either:

#!/usr/bin/python                                                               

import time
import sys
import curses

def alarmloop(stdscr):
    stdscr.addstr("How many seconds (alarm1)? ")
    curses.echo()
    alarm1 = int(stdscr.getstr())
    while (1):
        time.sleep(alarm1)
        curses.flushinp()
        stdscr.clear()
        stdscr.addstr("Alarm1\n")
        stdscr.addstr("Continue (Y/N)?[Y]:")
        doit = stdscr.getch()
        stdscr.addstr("\n")
        stdscr.addstr("Input "+chr(doit)+"\n")
        stdscr.refresh()
        if doit == ord('N') or doit == ord('n'):
            stdscr.addstr("Exiting.....\n")
            break

curses.wrapper(alarmloop)

EDIT: ah, Windows. Then you can use the msvcrt module. Note that the code below isn't perfect, and it doesn't work in IDLE at all:

#!/usr/bin/python

import time
import subprocess
import sys
import msvcrt

alarm1 = int(raw_input("How many seconds (alarm1)? "))

while (1):
    time.sleep(alarm1)
    print "Alarm1"
    sys.stdout.flush()

    # Try to flush the buffer
    while msvcrt.kbhit():
        msvcrt.getch()

    print "Continue (Y/N)?[Y]"
    doit = msvcrt.getch()
    print "Input",doit
    if doit == 'N' or doit=='n':
        print "Exiting....."
        break
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