从raw_input（）读取输入，而提示没有被Python中的其他线程覆盖

小编典典

从raw_input（）读取输入，而提示没有被Python中的其他线程覆盖

python

我试图让用户使用raw_input（）在控制台上输入命令，这很好。问题是我有一些后台线程，偶尔将日志信息输出到屏幕上，并且当他们这样做时，它们会弄乱输入提示（因为输出到当前光标所在的位置）。

这是一个小的Python程序，它说明了我的意思。

#!/usr/bin/env python
import threading
import time

def message_loop():
    while True:
        time.sleep(1)
        print "Hello World"

thread = threading.Thread(target = message_loop)
thread.start()

while True:
    input = raw_input("Prompt> ")
    print "You typed", input

这是运行时的外观示例：

Prompt> Hello World
Hello World
Hello World
Hello World
test
You typed test
Prompt> Hello World
Hello World
Hello World
hellHello World
o
You typed hello
Prompt> Hello World
Hello World
Hello World
Hello World

我想要的是提示与线程的输出一起移动。像这样：

Hello World
Hello World
Prompt> test
You typed test
Hello World
Hello World
Hello World
Hello World
Hello World
Prompt> hello
You typed hello
Hello World
Hello World
Hello World
Hello World
Prompt>

关于如何在不使用丑陋的黑客手段的情况下实现这一目标的任何想法？:)

阅读 219

2020-12-20

共1个答案

小编典典

我最近遇到了这个问题，并希望将此解决方案留在这里以备将来参考。这些解决方案从终端清除待处理的raw_input（readline）文本，打印新文本，然后将raw_input缓冲区中的内容重新打印到终端。

第一个程序非常简单，但是仅在只有一行文本等待raw_input时才能正确运行：

#!/usr/bin/python

import time,readline,thread,sys

def noisy_thread():
    while True:
        time.sleep(3)
        sys.stdout.write('\r'+' '*(len(readline.get_line_buffer())+2)+'\r')
        print 'Interrupting text!'
        sys.stdout.write('> ' + readline.get_line_buffer())
        sys.stdout.flush()

thread.start_new_thread(noisy_thread, ())
while True:
    s = raw_input('> ')

输出：

$ ./threads_input.py
Interrupting text!
Interrupting text!
Interrupting text!
> WELL, PRINCE, Genoa and Lucca are now no more than private estates of the Bo
Interrupting text!
> WELL, PRINCE, Genoa and Lucca are now no more than private estates of the Bo
naparte family. No, I warn you, that if you do not tell me we are at war,

第二个可以正确处理2条或更多的缓冲行，但是具有更多（标准）模块依赖性，并且需要一点点终端黑客：

#!/usr/bin/python

import time,readline,thread
import sys,struct,fcntl,termios

def blank_current_readline():
    # Next line said to be reasonably portable for various Unixes
    (rows,cols) = struct.unpack('hh', fcntl.ioctl(sys.stdout, termios.TIOCGWINSZ,'1234'))

    text_len = len(readline.get_line_buffer())+2

    # ANSI escape sequences (All VT100 except ESC[0G)
    sys.stdout.write('\x1b[2K')                         # Clear current line
    sys.stdout.write('\x1b[1A\x1b[2K'*(text_len/cols))  # Move cursor up and clear line
    sys.stdout.write('\x1b[0G')                         # Move to start of line


def noisy_thread():
    while True:
        time.sleep(3)
        blank_current_readline()
        print 'Interrupting text!'
        sys.stdout.write('> ' + readline.get_line_buffer())
        sys.stdout.flush()          # Needed or text doesn't show until a key is pressed


if __name__ == '__main__':
    thread.start_new_thread(noisy_thread, ())
    while True:
        s = raw_input('> ')

输出。先前的readline行已正确清除：

$ ./threads_input2.py
Interrupting text!
Interrupting text!
Interrupting text!
Interrupting text!
> WELL, PRINCE, Genoa and Lucca are now no more than private estates of the Bo
naparte family. No, I warn you, that if you do not tell me we are at war,

2020-12-20