子进程调用中的意外缩进

Question

我的印象是 exit(0) 向 Python 解释器发出信号 return 0 到系统。例如，

from subprocess import check_call
check_call('python3 -c "exit(0)"', shell=True)  # returns 0

但是

check_call(['/usr/bin/python3', '-c "exit(0)"'])

returns 1:

>>> check_call(['/usr/bin/python3', '-c "exit(0)"'])
  File "<string>", line 1
    "exit(0)"
    ^
IndentationError: unexpected indent
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.5/subprocess.py", line 581, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/bin/python3', '-c "exit(0)"']' returned non-zero exit status 1

我不知道哪里有空间偷偷溜进来，这是怎么回事？

Answer 1

看来，如果 -c 标志后面没有另一个参数，则当前参数的其余部分将被解释为 Python 代码：

>> python3 -c 'print("yes")'
yes

>> python3 '-cprint("yes")'
yes

>> python3 '-c print("yes")'
  File "<string>", line 1
    print("yes")
    ^
IndentationError: unexpected indent

所以下面两个应该都有效，虽然第一个变体感觉最idiomatic/safe：

check_call(['/usr/bin/python3', '-c', 'exit(0)'])
check_call(['/usr/bin/python3', '-cexit(0)'])

子进程调用中的意外缩进

Unexpected indent in subprocess call

python

bash

subprocess

indentation