Issue 243 - python-nose - sys.stdout modification interferes with output collection

Issue 243:	sys.stdout modification interferes with output collection	‹ Prev 65 of 305 Next ›
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Status:	Invalid
Owner:	----
Closed:	Mar 2009

Reported by gregg.lind, Mar 06, 2009

What steps will reproduce the problem?

------------------
# nose_test.py
import sys
import os
sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)

def test():
    assert 1
--------------------------

$nosetests nose_test.py     # throws error
$nosetests -s nose_test.py  # runs fine


What is the expected output? What do you see instead?

expected:  OK
instead:  

nosetests
E
======================================================================
ERROR: Failure: AttributeError ('cStringIO.StringO' object has no attribute
'fileno')
----------------------------------------------------------------------
Traceback (most recent call last):
  File
"/usr/lib/python2.4/site-packages/nose-0.10.4-py2.4.egg/nose/loader.py",
line 363, in loadTestsFromName
    module = self.importer.importFromPath(
  File
"/usr/lib/python2.4/site-packages/nose-0.10.4-py2.4.egg/nose/importer.py",
line 39, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File
"/usr/lib/python2.4/site-packages/nose-0.10.4-py2.4.egg/nose/importer.py",
line 84, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/nfs/data/home/gregg/local/src/gits/oui/trunk/nose_test.py", line
3, in ?
    sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)
AttributeError: 'cStringIO.StringO' object has no attribute 'fileno'

----------------------------------------------------------------------


What version of the product are you using? On what operating system?

nosetests version 0.10.4
Linux FC5 on x64

Comment 1 by jpellerin, Mar 06, 2009

If you want to capture sys.stdout yourself, you should turn off nose's capturing of
it with the --nocapture flag.

Status: Invalid

Comment 2 by gregg.lind, Mar 06, 2009

I don't want to capture output myself. I want nosetests to automatically sniff out my
tests.  When sys.stdout is changed to nobuffer in this way, nosetests fails.

Comment 3 by jpellerin, Mar 06, 2009

nosetests is failing because when nose's output capture is enabled, sys.stdout
doesn't have a fileno, because it's just a StringIO buffer -- like the exception
says. If you want this to work when output capture is enabled, you'll have to find
some other way to do what you're trying to do, or submit a patch implementing output
capture with a buffer that behaves more like a real file. Without a patch, I can't
prioritize changing nose's behavior, sorry.

Comment 4 by gregg.lind, Mar 06, 2009

Thank you, that is quite a helpful response.  

Specifically, the standard library docs say:  

fileno( ) 

***Note: File-like objects which do not have a real file descriptor should not
provide this method!*** 


Here is workaround code:
-----
import sys
import os

try:   # get unbuffered output
    sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)
except AttributeError, exc: # under nose, sys.stdout is reassigned to a string buffer
    pass
    

def test():
    assert 1