[IPython-User] Windows GUI only (pythonw) bug for IPython on Python 3.x

Brandon Parsons brandon@parsonstx....
Wed Jan 4 02:55:05 CST 2012


Trying to launch the ipython-qtconsole.exe or ipython-qtconsole-script.pyw
via pythonw on Python 3.2 immediately exits, and the Qt console never
starts.  Running with ipython-qtconsole-script.pyw with plain python.exe
works fine (and consumes the console). Fortunately, redirection stdout and
stderr allows to get the traceback (well, stderr is where it went), which
yields the following:

Traceback (most recent call last):
  File "\Python32\Scripts\ipython3-qtconsole-script.pyw", line 9, in
<module>
    load_entry_point('ipython==0.12', 'gui_scripts', 'ipython3-qtconsole')()
  File
"C:\Python32\lib\site-packages\distribute-0.6.24-py3.2.egg\pkg_resources.py",
line 337, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File
"C:\Python32\lib\site-packages\distribute-0.6.24-py3.2.egg\pkg_resources.py",
line 2280, in load_entry_point
    return ep.load()
  File
"C:\Python32\lib\site-packages\distribute-0.6.24-py3.2.egg\pkg_resources.py",
line 1990, in load
    entry = __import__(self.module_name, globals(),globals(), ['__name__'])
  File "C:\Python32\lib\site-packages\IPython\__init__.py", line 43, in
<module>
    from .config.loader import Config
  File "C:\Python32\lib\site-packages\IPython\config\loader.py", line 27,
in <module>
    from IPython.utils.path import filefind, get_ipython_dir
  File "C:\Python32\lib\site-packages\IPython\utils\path.py", line 24, in
<module>
    from IPython.utils.process import system
  File "C:\Python32\lib\site-packages\IPython\utils\process.py", line 25,
in <module>
    from ._process_win32 import _find_cmd, system, getoutput, AvoidUNCPath,
arg_split
  File "C:\Python32\lib\site-packages\IPython\utils\_process_win32.py",
line 30, in <module>
    from . import text
  File "C:\Python32\lib\site-packages\IPython\utils\text.py", line 30, in
<module>
    from IPython.utils.io import nlprint
  File "C:\Python32\lib\site-packages\IPython\utils\io.py", line 90, in
<module>
    stdin = IOStream(sys.stdin)
  File "C:\Python32\lib\site-packages\IPython\utils\io.py", line 32, in
__init__
    raise ValueError("fallback required, but not specified")
ValueError: fallback required, but not specified

I was confused why nobody had seen this before, but come to find out it's a
Python 3 vs 2 issue.  sys.std* are now None for pythonw processes in Python
3.x, while they were file objects with fileno == -2 on Python 2.x.  Regular
old prints will work when stdout/stderr are None, but they just get
discarded immediately, but of course any attribute lookups are going to
fail.

This simple script run with pythonw (on v2 and v3) highlights the
difference:
# this will show what the std* file handles are on Python 2.x vs Python 3.x
# noted @ http://bugs.python.org/issue1415
import sys

fname = 'python%d_std_fds.txt' % (sys.version_info[0])
f = open(fname, 'w')

if sys.stdin is None:
    f.write("stdin: None\n")
else:
    f.write("stdin: %i\n" % sys.stdin.fileno())
if sys.stdout is None:
    f.write("stdout: None\n")
else:
    f.write("stdout: %i\n" % sys.stdout.fileno())
if sys.stderr is None:
    f.write("stderr: None\n")
else:
    f.write("stderr: %i\n" % sys.stderr.fileno())
f.close()

brandon
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