subprocess.run()用法python3.7

def run(*popenargs,
        input=None, capture_output=False, timeout=None, check=False, **kwargs):
    """Run command with arguments and return a CompletedProcess instance.

    The returned instance will have attributes args, returncode, stdout and
    stderr. By default, stdout and stderr are not captured, and those attributes
    will be None. Pass stdout=PIPE and/or stderr=PIPE in order to capture them.

    If check is True and the exit code was non-zero, it raises a
    CalledProcessError. The CalledProcessError object will have the return code
    in the returncode attribute, and output & stderr attributes if those streams
    were captured.

    If timeout is given, and the process takes too long, a TimeoutExpired
    exception will be raised.

    There is an optional argument "input", allowing you to
    pass bytes or a string to the subprocess‘s stdin.  If you use this argument
    you may not also use the Popen constructor‘s "stdin" argument, as
    it will be used internally.

    By default, all communication is in bytes, and therefore any "input" should
    be bytes, and the stdout and stderr will be bytes. If in text mode, any
    "input" should be a string, and stdout and stderr will be strings decoded
    according to locale encoding, or by "encoding" if set. Text mode is
    triggered by setting any of text, encoding, errors or universal_newlines.

    The other arguments are the same as for the Popen constructor.
    """
    if input is not None:
        if ‘stdin‘ in kwargs:
            raise ValueError(‘stdin and input arguments may not both be used.‘)
        kwargs[‘stdin‘] = PIPE

    if capture_output:
        if (‘stdout‘ in kwargs) or (‘stderr‘ in kwargs):
            raise ValueError(‘stdout and stderr arguments may not be used ‘
                             ‘with capture_output.‘)
        kwargs[‘stdout‘] = PIPE
        kwargs[‘stderr‘] = PIPE

    with Popen(*popenargs, **kwargs) as process:
        try:
            stdout, stderr = process.communicate(input, timeout=timeout)
        except TimeoutExpired:
            process.kill()
            stdout, stderr = process.communicate()
            raise TimeoutExpired(process.args, timeout, output=stdout,
                                 stderr=stderr)
        except:  # Including KeyboardInterrupt, communicate handled that.
            process.kill()
            # We don‘t call process.wait() as .__exit__ does that for us.
            raise
        retcode = process.poll()
        if check and retcode:
            raise CalledProcessError(retcode, process.args,
                                     output=stdout, stderr=stderr)
    return CompletedProcess(process.args, retcode, stdout, stderr)

class CompletedProcess(object):
    """A process that has finished running.

    This is returned by run().

    Attributes:
      args: The list or str args passed to run().
      returncode: The exit code of the process, negative for signals.
      stdout: The standard output (None if not captured).
      stderr: The standard error (None if not captured).
    """
    def __init__(self, args, returncode, stdout=None, stderr=None):
        self.args = args
        self.returncode = returncode
        self.stdout = stdout
        self.stderr = stderr

    def __repr__(self):
        args = [‘args={!r}‘.format(self.args),
                ‘returncode={!r}‘.format(self.returncode)]
        if self.stdout is not None:
            args.append(‘stdout={!r}‘.format(self.stdout))
        if self.stderr is not None:
            args.append(‘stderr={!r}‘.format(self.stderr))
        return "{}({})".format(type(self).__name__, ‘, ‘.join(args))

    def check_returncode(self):
        """Raise CalledProcessError if the exit code is non-zero."""
        if self.returncode:
            raise CalledProcessError(self.returncode, self.args, self.stdout,
                                     self.stderr)