Programming Forums > Script Programming > Python

Sane · May 31st, 2006, 11:21 PM

I need to redirect all console output (including error messages) to a log file. There are several reasons why I would have to go out of my way to change each print statement to a call to a function. It would be much easier if there's some support in the sys library for just that?

Any helpful info?

hydroxide · Jun 1st, 2006, 12:12 AM

Quote:

Originally Posted by Sane

I need to redirect all console output (including error messages) to a log file. There are several reasons why I would have to go out of my way to change each print statement to a call to a function. It would be much easier if there's some support in the sys library for just that?

Any helpful info?

It's not a great way of doing things, but you can just set sys.stdout to your logfile:

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import sys
oldstdout = sys.stdout     # So you can restore later
sys.stdout = file("C:/temp/test.txt", "w")  # Or whatever your logfile is
for i in range(10):
    print "Hello", i
sys.stdout.close()
sys.stdout = oldstdout

An alternative might be to do a find and replace of all instances of "print " to "print>>STDERR,". Then at the top of your module or config file define STDERR as your logfile. If you want to have things print to screen then change STDERR to sys.stderr.

Another alternative would be to import logging and actually log things properly rather than using prints.

-T.

Cerulean · Jun 1st, 2006, 1:00 PM

You generally do this from the command line. Not sure if this is the same with windows (doubtful) but under Linux (with BASH) you generally do

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python foo.py > logfile.txt 2>&1

The `2>&1` bit redirects stderr into stdout, and the `> logfile.txt` bit redirects stdout into logfile.txt.
If you're writing to stderr from your Python program then you want to just set sys.stderr to sys.stdout at the top of your source file, which will effectively 'redirect' everything to STDOUT.

megamind5005 · Jun 1st, 2006, 4:56 PM

The "> file.ex" thing does work in windows as does the "< input.ex" for providing automatic input. Didnt know about the "2>&1" ... where abouts can I find some documentation on it, Cerulean?

May 31st, 2006, 11:21 PM	#1
Sane Programming Guru Join Date: Apr 2005 Posts: 1,799 Rep Power: 5	Redirecting Console Output I need to redirect all console output (including error messages) to a log file. There are several reasons why I would have to go out of my way to change each print statement to a call to a function. It would be much easier if there's some support in the sys library for just that? Any helpful info?

Jun 1st, 2006, 1:00 PM	#3
Cerulean Professional Programmer Join Date: Apr 2005 Location: London, England Posts: 459 Rep Power: 4	You generally do this from the command line. Not sure if this is the same with windows (doubtful) but under Linux (with BASH) you generally do (Toggle Plain Text) python foo.py > logfile.txt 2>&1 python foo.py > logfile.txt 2>&1 The `2>&1` bit redirects stderr into stdout, and the `> logfile.txt` bit redirects stdout into logfile.txt. If you're writing to stderr from your Python program then you want to just set sys.stderr to sys.stdout at the top of your source file, which will effectively 'redirect' everything to STDOUT.

Jun 1st, 2006, 4:56 PM	#4
megamind5005 Programmer Join Date: Dec 2004 Location: UK Posts: 53 Rep Power: 4	The "> file.ex" thing does work in windows as does the "< input.ex" for providing automatic input. Didnt know about the "2>&1" ... where abouts can I find some documentation on it, Cerulean? __________________ Tetris is so unrealistic

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Programming Forums > Script Programming > Python

Redirecting Console Output