why am I getting IOError: (9, 'Bad file descriptor') error while making print statements?

Question

I am running a python2.5 script on a windows 2003 server as a service. I am getting this error for simple print statments:

IOError: (9, \'Bad file descriptor         


        

Answer 1

You can't print because sys.stdout is not available when not running as a console session.

Instead of using print statements you can consider using the logging module so you can set the loglevel and write all critical things to the system event log.

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It should be noted that you can still get it to work (or silently ignore the problem) by doing something like this:

To write to a file per output stream:

import sys
sys.stdout = open('stdout.txt', 'w')
sys.stderr = open('stderr.txt', 'w')

To write to a single file:

import sys
sys.stdout = sys.stderr = open('output.txt', 'w')

Or to silently ignore all print statements:

import sys
class NullWriter(object):
    def write(self, value): pass

sys.stdout = sys.stderr = NullWriter()

Answer 2

In Python 2.x, this is the expected behavior. In this bug report, Christian Heimes explains that it is a design decision:

I recommend against changing the code so late in the Python 2.7 release cycle. A change in behavior is too confusing. And it's not a bug but a design decision, too. Over five years ago I implement parts of the IO interaction with the operating system for Python 3.0. I deliberately did NOT port modifications to 2.6.

He also recommends a workaround for obtaining Python 3.x-style print() behavior in Python 2.7:

from __future__ import print_function
import sys
if sys.executable.endswith("pythonw.exe"):
    sys.stdout = sys.stdout = None

print("can handle sys.stdout = None just fine.")