using print() with multiprocessing and pythonw

[Isaac Gerg]

I launch my program with pythonw and begin it with the code below so that all 
my print()'s go to the log file specified. 

if sys.executable.find('pythonw') =0:
# Redirect all console output to file.
sys.stdout = open(pythonw - stdout stderr.log,'w')
sys.stderr = sys.stdout

During the course of my program, I call multiprocessing.Process() and launch a 
function several times.  That function has print()'s inside (which are from 
warnings being printed by python).  This printing causes the multiprocess to 
crash.  How can I fix my code so that the print()'s are supressed. I would hate 
to do a warnings.filterwarnings('ignore') because when I unit test those 
functions, the warnings dont appear.

Thanks in advance,
Isaac
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Re: using print() with multiprocessing and pythonw

[William Ray Wing]

On Nov 12, 2013, at 2:12 PM, Isaac Gerg isaac.g...@gergltd.com wrote:

 I launch my program with pythonw and begin it with the code below so that all 
 my print()'s go to the log file specified. 
 
 if sys.executable.find('pythonw') =0:
# Redirect all console output to file.
sys.stdout = open(pythonw - stdout stderr.log,'w')
sys.stderr = sys.stdout
 
 During the course of my program, I call multiprocessing.Process() and launch 
 a function several times.  That function has print()'s inside (which are from 
 warnings being printed by python).  This printing causes the multiprocess to 
 crash.  How can I fix my code so that the print()'s are supressed. I would 
 hate to do a warnings.filterwarnings('ignore') because when I unit test those 
 functions, the warnings dont appear.
 
 Thanks in advance,
 Isaac
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 https://mail.python.org/mailman/listinfo/python-list

This may be inelegant, but it solved a similar problem for me.  Replace the 
print statements with logging.info statements and have each invocation of the 
function dump to a unique log file (with a name based on the function's input). 
 At least in my case, multiprocessing seemed to get its feet tangled (crash) 
when different subprocesses tried to print to the same output file at the same 
time.

-Bill
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Re: using print() with multiprocessing and pythonw

[Isaac Gerg]

Thanks for the reply Bill.  The problem is the text i am getting is from a 
python warning message, not one of my own print() function calls.
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Re: using print() with multiprocessing and pythonw

[Chris Angelico]

On Wed, Nov 13, 2013 at 7:22 AM, Isaac Gerg isaac.g...@gergltd.com wrote:
 Thanks for the reply Bill.  The problem is the text i am getting is from a 
 python warning message, not one of my own print() function calls.

Since sys.stdout is just an object, you could replace it with
something that redirects its write() calls to the logging function.
Might be a bit hacky, but it should work.

BTW, sys.executable.find('pythonw') =0 should be able to be spelled
'pythonw' in sys.executable.

ChrisA
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