python - 从 os.system 调用 shell 命令不起作用

Question

我对 python 很陌生，我有这样的代码：

os.system(''' PROMPT_COMMAND="printf '%*s\n' "${COLUMNS:-$(tput cols)}" '' | tr ' ' -" ''')

那个部分：

PROMPT_COMMAND="printf '%*s\n' "${COLUMNS:-$(tput cols)}" '' | tr ' ' -"

确实打印-以填充外壳宽度。上述命令在命令提示符下按预期工作。但是当我在python中做的时候。我根本没有输出。

Answer 1

There is no point of issuing this command at all.

As I understand it, you are just setting the environment variable PROMPT_COMMAND in order to make the shell execute it on every prompt.

But setting an environment variable has only an impact of a called shell, but not to the caller. You cannot change the environment of your parent process.

Answer 2

这会做。正如我所看到的，问题在于引号：

import os

PROMPT_COMMAND = 'printf "%*s\n" "${COLUMNS:-$(tput cols)}" "" | tr " " -'
os.system(PROMPT_COMMAND)