Python - 无限循环，中断用户输入
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Python - Infinite while loop, break on user input
提问by TehTechGuy
I have an infinite while loop that I want to break out of when the user presses a key. Usually I use raw_inputto get the user's response; however, I need raw_inputto not wait for the response. I want something like this:
我有一个无限的 while 循环，我想在用户按下某个键时跳出它。通常我raw_input用来获取用户的响应；但是，我不需要raw_input等待响应。我想要这样的东西：
print 'Press enter to continue.'
while True:
# Do stuff
#
# User pressed enter, break out of loop
This should be a simple, but I can't seem to figure it out. I'm leaning towards a solution using threading, but I would rather not have to do that. How can I accomplish this?
这应该是一个简单的，但我似乎无法弄清楚。我倾向于使用线程的解决方案，但我宁愿不必这样做。我怎样才能做到这一点？
采纳答案by octref
I think you can do better with msvcrt:
我认为你可以用 msvcrt 做得更好：
import msvcrt, time
i = 0
while True:
i = i + 1
if msvcrt.kbhit():
if msvcrt.getwche() == '\r':
break
time.sleep(0.1)
print(i)
Sadly, still windows-specific.
可悲的是，仍然是特定于 Windows 的。
回答by TehTechGuy
Using the msvcrtmodule as thebjornrecommended I was able to come up with something that works. The following is a basic example that will exit the loop if any key is pressed, not just enter.
使用thebjorn推荐的msvcrt模块，我能够想出一些有用的东西。以下是一个基本示例，如果按下任何键，则将退出循环，而不仅仅是输入。
import msvcrt, time
i = 0
while True:
i = i + 1
if msvcrt.kbhit():
break
time.sleep(0.1)
print i
回答by micromoses
You can use non-blocking read from stdin:
您可以使用非阻塞从标准输入读取：
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)
回答by moisesvega
What you need is a non-blocking raw input, if you don't want to use threads there is a simple solution like this one below where he is doing a timeout of 20 ms and then raise and exception if the user doesn't press a key, if he does then the class returns the key pressed.
你需要的是一个非阻塞的原始输入，如果你不想使用线程，那么有一个像下面这样的简单解决方案，他正在做 20 毫秒的超时，然后如果用户不按，则引发和异常一个键，如果他这样做了，那么班级会返回按下的键。
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 ''
回答by gtcoder
On python 3.5 you can use the following code. It can be adjusted for a specific keystroke. The while loop will keep running until the user presses a key.
在 python 3.5 上，您可以使用以下代码。它可以针对特定的击键进行调整。while 循环将一直运行，直到用户按下某个键。
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()
回答by pratyay
I could not get some of the popular answers working. So I came up with another approach using the CTRL+ Cto plug in user input and imbibe a keyboard interrupt. A simple solution can be using a try-catch block,
我无法得到一些流行的答案。所以我想出了另一种方法，使用CTRL+C来插入用户输入并吸收键盘中断。一个简单的解决方案是使用 try-catch 块，
i = 0
try:
while True:
i+=1
print(i)
sleep(1)
except:
pass
# do what you want to do after it...
I got this idea from running a number of servers like flask and django. This might be slightly different from what the OP asked, but it might help someone else who wanted a similar thing.
我从运行多个服务器（如 Flask 和 django）中得到了这个想法。这可能与 OP 所要求的略有不同，但它可能会帮助其他想要类似事情的人。
