Exiting while loop by pressing enter without block

问题:

So I've been doing a little bit of reading up on how to exit a while loop by the user pressing the enter key and I've come up with the following:

import sys, select, os

switch = 1
i = 1
while switch == 1:
    os.system('cls' if os.name == 'nt' else 'clear')
    print "I'm doing stuff. Press Enter to stop me!"
    print i
    while sys.stdin in select.select([sys.stdin], [], [], 0)[0]:
        line = raw_input()
        if not line:
            print "Finished! =]"
            switch = 0
        else:
            print "Finished! =]"
            switch = 0
    i = i+1

Is there a way to tidy this up? In particular the "if not line" and the following "else" look messy. Can they be combined into one? A better alternative to using "switch"?

Initially if I typed a bunch of characters and then hit enter it didn't stop the loop. I would have to press enter again. The if not and else components are intended to set it up such that it would exit on the first press of enter.

回答1:

This worked for me:

import sys, select, os

i = 0
while True:
    os.system('cls' if os.name == 'nt' else 'clear')
    print "I'm doing stuff. Press Enter to stop me!"
    print i
    if sys.stdin in select.select([sys.stdin], [], [], 0)[0]:
        line = raw_input()
        break
    i += 1

You only need to check for the stdin being input once (since the first input will terminate the loop). If the conditions line/not line have result for you, you can combine them to one if statement. Then, with only one while statement being used, you can now use break instead of setting a flag.