Python - endless while loop interrupting user input

Question

I have an infinite while loop that I want to exit when the user presses a key. I usually use raw_inputto get the user's response; however, I need raw_inputnot wait for an answer. I want something like this:

print 'Press enter to continue.'
while True:
    # Do stuff
    #
    # User pressed enter, break out of loop

It should be simple, but I can't figure it out. I am inclined towards a solution using threads, but I would prefer not to. How can i do this?

Answer 1

I think you can do better with msvcrt:

import msvcrt, time
i = 0
while True:
    i = i + 1
    if msvcrt.kbhit():
        if msvcrt.getwche() == '\r':
            break
    time.sleep(0.1)
print(i)

Unfortunately, it still depends on the window.

Answer 2

You can use non-blocking reading from stdin:

import sys
import os
import fcntl
import time

fl = fcntl.fcntl(sys.stdin.fileno(), fcntl.F_GETFL)
fcntl.fcntl(sys.stdin.fileno(), fcntl.F_SETFL, fl | os.O_NONBLOCK)
while True:
    print("Waiting for user input")
    try:
        stdin = sys.stdin.read()
        if "\n" in stdin or "\r" in stdin:
            break
    except IOError:
        pass
    time.sleep(1)

Answer 3

python 3.5 . . while , .

import time
import threading

# set global variable flag
flag = 1

def normal():
    global flag
    while flag==1:
        print('normal stuff')
        time.sleep(2)
        if flag==False:
            print('The while loop is now closing')


def get_input():
    global flag
    keystrk=input('Press a key \n')
    # thread doesn't continue until key is pressed
    print('You pressed: ', keystrk)
    flag=False
    print('flag is now:', flag)

n=threading.Thread(target=normal)
i=threading.Thread(target=get_input)
n.start()
i.start()

Answer 4

msvcrt thebjorn, -, . , , , .

import msvcrt, time
i = 0
while True:
    i = i + 1
    if msvcrt.kbhit():
        break
    time.sleep(0.1)
print i

Answer 5

- , , , , - 20 , , 't , , .

import signal

class AlarmException(Exception):
    pass

def alarmHandler(signum, frame):
    raise AlarmException

def nonBlockingRawInput(prompt='', timeout=20):
    signal.signal(signal.SIGALRM, alarmHandler)
    signal.alarm(timeout)
    try:
        text = raw_input(prompt)
        signal.alarm(0)
        return text
    except AlarmException:
        print '\nPrompt timeout. Continuing...'
    signal.signal(signal.SIGALRM, signal.SIG_IGN)
    return ''

Answer 6

. , CTRL + C . try-catch,

i = 0
try:
    while True:
        i+=1
        print(i)
        sleep(1)
except:
    pass
# do what you want to do after it...

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