Question

我正在编写一个需要显式解析所有键盘输入的python应用程序。因此我写了一个小循环，不断读取标准输入。这很好，但是，stdin.read（1）会阻塞，直到我们输入一个字符。现在我希望它在（例如）1秒后超时，以便其他事情发生。我在python中读到了select模块，现在我有以下内容：

def getch(timeout):                                                                                                                                          
    fd = sys.stdin.fileno()                                                                                                                                   
    old_settings = termios.tcgetattr(fd)                                                                                                                      
    ch = None                                                                                                                                                 
    try:                                                                                                                                                      
        tty.setraw(fd)                                                                                                                                        
        rlist, _, _ = select([sys.stdin], [], [], timeout)                                                                                                    
        if len(rlist) > 0:                                                                                                                                    
            ch = sys.stdin.read(1)                                                                                                                            
    finally:                                                                                                                                                  
        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)                                                                                                
    return ch

这段代码的问题是，当我按箭头键时，我只收到'\ x1b'。 select函数永远不会触发剩余的'['和'D'。

如何正确阅读这些箭头键字符？或者如何再次使select函数触发（因为stdin上仍有数据可用）。

谢谢！

Answer 1

方向键是 ANSI scape sequences。它们以 Escape（十六进制：\x1b，八进制：\033，十进制：27）开头，后跟括号 [。以下是关键代码：

import sys, termios, tty

esc = 27
up = "\033[A"
down = "\033[B"
right = "\033[C"
left = "\033[D"

if __name__ == "__main__":
    fd_input = sys.stdin.fileno()
    
    # save previous terminal attributes
    term_attrs_old = termios.tcgetattr(fd_input)
    
    # Set terminal to raw mode. It gives you back what ever was typed,
    # as raw bytes without any processing
    tty.setraw(fd_input)

    # read 4 bytes and encode it
    ch = sys.stdin.buffer.raw.read(4).decode(sys.stdin.encoding)

    if len(ch) == 1:
        # if it is 1 char, and non-printable, return its Unicode code
        if ord(ch) < 32 or ord(ch) > 126:
            ch = ord(ch)
    
    elif ord(ch[0]) == 27:
        # if the input is more that 1 char and it starts with 27, 
        # user has entered a scape sequence
        # read its rest
        ch = "\033" + ch[1:]
        if ch == down:
            ch = "down"
        if ch == up:
            ch = "up"
        if ch == right:
            ch = "right"
        if ch == left:
            ch = "left"
    
    # reset terminal back to its setting (disable raw mode again)
    termios.tcsetattr(fd_input, termios.TCSADRAIN, term_attrs_old)
    print(ch)

从stdin读取而不阻塞

1 个答案: