Subprocess: 意外的关键字参数 catch_output

当执行巨蟒文件中给出的 subprocess.run()时，我得到一个 TypeError:

>>> import subprocess
>>> subprocess.run(["ls", "-l", "/dev/null"], capture_output=True)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.6/subprocess.py", line 403, in run
with Popen(*popenargs, **kwargs) as process:
TypeError: __init__() got an unexpected keyword argument 'capture_output'

我正在运行 Python 3.6。6:

$ python3 --version
Python 3.6.6

57904

小开

最佳答案

You inspected the wrong documentation, for python-3.6 this parameter does not exist, as can be found in the documentation (you select the version at the top left):

subprocess.run(args, *, stdin=None, input=None, stdout=None, stderr=None,
shell=False, cwd=None, timeout=None, check=False, encoding=None,
errors=None, env=None)

You can however easily "emulate" this by setting both stdout and stderr to PIPE:

from subprocess import PIPE


subprocess.run(["ls", "-l", "/dev/null"], stdout=PIPE, stderr=PIPE)

In fact, if we look at the source code of the python-3.7 version, where the feature was introduced, we see in the source code [GitHub]:

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