python subprocess with failed command return code 0

Question

I execute the following code in both windows cmd and ubuntu bash:

python -c "import xxx"

Error messages output. And when I run:

echo $? / echo %errorlevel%

The value is 1.

When I do the same task in python script with subprocess as follows:

cmdlst = ['python', '-c', '"import xxx"‘]
proc = subprocess.Popen(cmdlst)
retcode = proc.wait()

The retcode is 0. What is the problem and how can I get the correct return code of the command run within a subprocess.

Thanks in advance.

• Charles Duffy: Huh? The "smart quotes" you're using here aren't valid syntax at all.
• Charles Duffy: (that is to say, '"import xxx"‘ is a very different thing from '"import xxx"', and the former -- which is what is included in the question -- wouldn't exit with status 0).

Answer 1

Running the shell command (equivalent to your given subprocess.Popen() call if we disregard the use of "smart quotes")

'python' '-c' '"import xxx"'

correctly exits with status 0, whether or not a module named xxx exists.

This is because "import xxx" is a string, and evaluating a string does not throw an exception. You'd get the exact same behavior from python -c '"hello world"', or any other string.

---

If you really want to try executing the code import xxx, then you need to remove the extra quotes:

subprocess.Popen(['python', '-c', 'import xxx']).wait()

...will properly return 1 (if no xxx module exists).

• yoctold: I've got it. Thanks