Python implements the function of pressing any key to continue/exit

Preface

To implement this function, all you need is to pause the program, wait and capture a keyboard input from the user, and then continue execution. Python has built-in libraries that can help us implement this function, but Windows and Linux must be treated differently. The

getch()

method in msvcrt can help to implement it under Windows. Its function is to obtain a key response and return the corresponding character. It is not echoed on the command line. There is the following program segment:

import msvcrt
print ord(msvcrt.getch())

Here, ord is used to convert the obtained characters into ASCII values, such as capture Pressing the "d" key (note the lower case) will give you the value 100.

What about Linux? Well, it’s a little bit complicated, but it’ll be easier if you clarify your thoughts first.

First of all, you need to know the three modes of Linux terminal, which are standard mode, non-standard mode and raw mode:

Normal mode

Normal mode, also known as cooked mode, is a common mode for users. Characters entered by the driver are saved in a buffer, and these buffered characters are only sent to the program when the Enter key is received. Buffered data allows the driver to implement the most basic editing functions. The specific keys assigned to these functions are set in the driver and can be modified through the command stty or the system call tcsetattr .

Non-canonical mode

When the buffering and editing functions are turned off, the connection is placed in non-canonical mode. The terminal processor still performs specific character processing, such as handling conversions between Ctrl-C and newline characters, but the edit keys will have no meaning, so the corresponding input is treated as regular data input, and the program needs to implement the editing function itself.

raw mode

When all processing is turned off and the driver passes input directly to the program, the connection is called raw mode.

Here we need to resort to non-canonical mode, so to achieve similar behavior on Windows just now, we need the following code:

import os
import termios
 
# 获取标准输入的描述符
fd = sys.stdin.fileno()
 
# 获取标准输入(终端)的设置
old_ttyinfo = termios.tcgetattr(fd)
 
# 配置终端
new_ttyinfo = old_ttyinfo[:]
 
# 使用非规范模式(索引3是c_lflag 也就是本地模式)
new_ttyinfo[3] &= ~termios.ICANON
 
# 关闭回显(输入不会被显示)
new_ttyinfo[3] &= ~termios.ECHO
 
# 使设置生效
termios.tcsetattr(fd, termios.TCSANOW, new_ttyinfo)
 
# 从终端读取
print ord(os.read(fd, 7))

Therefore It seems that we only need to use the above method to capture a key response, and then continue the program to achieve the function of pressing any key to continue or exit. Of course, the function of pressing a specified key to continue or exit can also be implemented in a similar way, for example:

import msvcrt
 
print("Press 'D' to exit...")
 
while True:
 if ord(msvcrt.getch()) in [68, 100]:
  break

In this way, when the user presses "D" or "d", the program exits.

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