In python, can I redirect the output of print function to stderr?

Question

There're lots of print function (python 2.7) in my program. Is there any way I can add a few lines then all the output can be redirected to stderr? What I want is python codes but not linux pipeline.

For example, my program is like:

print 'hello world'

I would like to add some codes like:

redirect_output_to_stderr()
print 'hello world'

Then all the output can be redirected to stderr.

I know print >> sys.stderr, 'hello world' can achieve my goal, but is it any way that can prevent from modifying the existed codes?

The _only_ way to do that _without modifying the code_ is to use a shell's redirection commands. — Roland Smith, Apr 07 '13 at 08:42
Oh, I guess what I need is preventing from modified the existed `print` functions. Thank you for mentioned that :) — waitingkuo, Apr 07 '13 at 08:45

score 20 · Answer 1 · answered Apr 07 '13 at 08:38

20

In python 2.7 you can do:

import sys

print >> sys.stderr, "To stderr."

Or you can import the behavior from 3.x:

from __future__ import print_function
import sys

print('To stderr.', file=sys.stderr)

answered Apr 07 '13 at 08:38

Roland Smith

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score 8 · Accepted Answer · answered Apr 07 '13 at 08:31

8

Do this in your method:

import sys
sys.stdout = sys.stderr

answered Apr 07 '13 at 08:31

MostafaR

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Or maybe don't, god this is horrible advice. – ruohola Sep 05 '19 at 10:22
@ruohola Yeah, not a great thing to do in any code, even 6 years ago! But I guess this is exactly what the question was asking for ¯\_(ツ)_/¯ – MostafaR Sep 05 '19 at 15:05

score 1 · Answer 3 · edited May 23 '17 at 11:54

1

Redefinition of print is feature of Python 3+. However, you can change sys.stdout to std.stderr.

See: another question

edited May 23 '17 at 11:54

Community

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answered Apr 07 '13 at 08:32

kravemir

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You *can* redefine `print` in 2.7 if you do `from __future__ import print_function`. – lvc Apr 07 '13 at 08:44
@lvc Didn't know that. Still change of `stdout` is shorter than function redefinition. – kravemir Apr 07 '13 at 08:47

In python, can I redirect the output of print function to stderr?

3 Answers3

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