pythonstdoutstderrsuppressdev-null

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

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
Solution

  • 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: