如何以一般方式使 Python 函数运行的可执行文件的终端输出静音？

我想抑制运行可执行文件的函数产生的所有终端输出。

我尝试使用上下文管理器来抑制 Python 函数的输出，该上下文管理器在每次调用函数时临时重新定义 stdout 和 stderr。这抑制了由产生的终端输出print在函数中调用，但当函数调用产生终端输出的可执行文件时，它似乎不起作用。

那么，如何抑制 Python 函数调用的可执行文件的输出呢？

我的代码如下。我已经包含了一个调用的示例函数ls尝试说明我想要抑制的终端输出类型（尽管我正在处理的函数不同）。

#!/usr/bin/env python

import os
import subprocess
import sys

def main():

    print("hello")

    with silence():
        print("there")

    print("world")

    with silence():
        engage_command(command = "ls")

class silence(object):

    def __init__(
        self,
        stdout = None,
        stderr = None
        ):
        if stdout == None and stderr == None:
            devnull = open(os.devnull, "w")
            stdout = devnull
            stderr = devnull
        self._stdout = stdout or sys.stdout
        self._stderr = stderr or sys.stderr

    def __enter__(
        self
        ):
        self.old_stdout = sys.stdout
        self.old_stderr = sys.stderr
        self.old_stdout.flush()
        self.old_stderr.flush()
        sys.stdout = self._stdout
        sys.stderr = self._stderr

    def __exit__(
        self,
        exc_type,
        exc_value,
        traceback
        ):
        self._stdout.flush()
        self._stderr.flush()
        sys.stdout = self.old_stdout
        sys.stderr = self.old_stderr

def engage_command(
    command = None
    ):
    process = subprocess.Popen(
        [command],
        shell      = True,
        executable = "/bin/bash")
    process.wait()
    output, errors = process.communicate()
    return output

if __name__ == "__main__":
    main()

在我的特定情况下，我尝试运行以下函数（而不是ls上面的函数）：

with propyte.silence():
    stream = pyaudio.PyAudio().open(
        format   = pyaudio.PyAudio().get_format_from_width(1),
        channels = 1, 
        rate     = bitrate, 
        output   = True
    )

运行时，会产生如下输出：

ALSA lib pcm_dsnoop.c:606:(snd_pcm_dsnoop_open) unable to open slave
ALSA lib pcm_dmix.c:1029:(snd_pcm_dmix_open) unable to open slave
ALSA lib pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_dmix.c:1029:(snd_pcm_dmix_open) unable to open slave
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock

我想抑制该输出。

编辑：测试一个办法 https://stackoverflow.com/a/36966379/1556092由@Matthias 提供

#!/usr/bin/env python

import contextlib
import os
import subprocess
import sys

def main():

    print("hello")

    with silence():
        print("there")

    print("world")

    with silence():
        engage_command(command = "ls")

@contextlib.contextmanager
def silence():
    devnull = os.open(os.devnull, os.O_WRONLY)
    old_stderr = os.dup(2)
    sys.stderr.flush()
    os.dup2(devnull, 2)
    os.close(devnull)
    try:
        yield
    finally:
        os.dup2(old_stderr, 2)
        os.close(old_stderr)

def engage_command(
    command = None
    ):
    process = subprocess.Popen(
        [command],
        shell      = True,
        executable = "/bin/bash")
    process.wait()
    output, errors = process.communicate()
    return output

if __name__ == "__main__":
    main()

我没有成功地抑制终端输出print or the ls我不知道为什么。

您可以从 PyAudio 切换到声音装置 http://python-sounddevice.readthedocs.io/模块，它已经负责使终端输出静音（请参阅#12 https://github.com/spatialaudio/python-sounddevice/pull/12）。这是如何完成的（使用 CFFI）：

from cffi import FFI
import os

ffi = FFI()
ffi.cdef("""
/* from stdio.h */
FILE* fopen(const char* path, const char* mode);
int fclose(FILE* fp);
FILE* stderr;  /* GNU C library */
FILE* __stderrp;  /* Mac OS X */
""")
try:
    stdio = ffi.dlopen(None)
    devnull = stdio.fopen(os.devnull.encode(), b'w')
except OSError:
    return
try:
    stdio.stderr = devnull
except KeyError:
    try:
        stdio.__stderrp = devnull
    except KeyError:
        stdio.fclose(devnull)

如果你想要一个纯Python的解决方案，你可以尝试这个上下文管理器：

import contextlib
import os
import sys

@contextlib.contextmanager
def ignore_stderr():
    devnull = os.open(os.devnull, os.O_WRONLY)
    old_stderr = os.dup(2)
    sys.stderr.flush()
    os.dup2(devnull, 2)
    os.close(devnull)
    try:
        yield
    finally:
        os.dup2(old_stderr, 2)
        os.close(old_stderr)

这是一篇关于该主题的非常有用的博客文章：http://eli.thegreenplace.net/2015/redirecting-all-kinds-of-stdout-in-python/ http://eli.thegreenplace.net/2015/redirecting-all-kinds-of-stdout-in-python/.

UPDATE:

上面的上下文管理器静默标准错误输出（stderr），用于原始问题中提到的来自 PortAudio 的烦人消息。摆脱标准输出（stdout），正如在您更新的问题中一样，您必须替换sys.stderr with sys.stdout和文件描述符2与号码1:

@contextlib.contextmanager
def ignore_stdout():
    devnull = os.open(os.devnull, os.O_WRONLY)
    old_stdout = os.dup(1)
    sys.stdout.flush()
    os.dup2(devnull, 1)
    os.close(devnull)
    try:
        yield
    finally:
        os.dup2(old_stdout, 1)
        os.close(old_stdout)