How to use a `with` statement to suppress `sys.stdout` or `sys.stderr`?

Question

I'm trying to use a with statement to suppress sys.stdout or sys.stderr individually. I found a tutorial that didn't work. I'm using Python 3.6.4 and I think the tutorial is some version of Python 2.

I looked it up on SO and found a few but with applications that didn't work or did not apply to this situation.

This doesn't apply:Python subprocess supress stdout and stderr

Couldn't get any of the with statements to work: Suppress stdout / stderr print from Python functions

This is for fortran: Redirecting FORTRAN (called via F2PY) output in Python

from contextlib import contextmanager
@contextmanager
def suppress_console(file=sys.stdout):
    with open(os.devnull, "w") as devnull:
        old_file = file
        file = devnull
        try:  
            yield
        finally:
            file = old_file

with suppress_console():
    print(1, file=sys.stdout)
# 1

Answer 1

I use something like this:

class Suppress:
    def __init__(self, *, suppress_stdout=False, suppress_stderr=False):
        self.suppress_stdout = suppress_stdout
        self.suppress_stderr = suppress_stderr
        self.original_stdout = None
        self.original_stderr = None

    def __enter__(self):
        import sys, os
        devnull = open(os.devnull, "w")

        # Suppress streams
        if self.suppress_stdout:
            self.original_stdout = sys.stdout
            sys.stdout = devnull

        if self.suppress_stderr:
            self.original_stderr = sys.stderr
            sys.stderr = devnull

    def __exit__(self, *args, **kwargs):
        import sys
        # Restore streams
        if self.suppress_stdout:
            sys.stdout = self.original_stdout

        if self.suppress_stderr:
            sys.stderr = self.original_stderr

Example:

import sys
print("Before")
with Suppress(suppress_stdout=True):
    print("Inside")
print("After")

print("Before", file=sys.stderr)
with Suppress(suppress_stderr=True):
    print("Inside", file=sys.stderr)
print("After", file=sys.stderr)

Output:

Before
After
Before
After

Notes:

• I put my imports inside methods for cleanliness, but usually this would be inside a module file with imports at the top.
• Suppressing stderr is risky, especially because of the way I'm (not) handling exceptions in the __exit__ method. You might look into crafting a more robust exit method.

Answer 2

I use the following one:

from contextlib import redirect_stdout, contextmanager
import os


@contextmanager
def suppress():
    with open(os.devnull, "w") as null:
        with redirect_stdout(null):
            yield

test:

print("qwer")
with suppress():
    print("asdf")
print("ghjk")
# qwer
# ghjk

update

A better one:

from contextlib import redirect_stdout, redirect_stderr, contextmanager, ExitStack
import os

@contextmanager
def suppress(out=True, err=False):
    with ExitStack() as stack:
        with open(os.devnull, "w") as null:
            if out:
                stack.enter_context(redirect_stdout(null))
            if err:
                stack.enter_context(redirect_stderr(null))
            yield