Issue 24920: shutil.get_terminal_size throws AttributeError

OS: windows 7, python 3.4.3, tk version 8.6.1

os.get_terminal_size also fails.


>>> shutil.get_terminal_size()
Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    shutil.get_terminal_size()
  File "C:\Python34\lib\shutil.py", line 1058, in get_terminal_size
    size = os.get_terminal_size(sys.__stdout__.fileno())
AttributeError: 'NoneType' object has no attribute 'fileno'
>>> os.get_terminal_size()
Traceback (most recent call last):
  File "<pyshell#5>", line 1, in <module>
    os.get_terminal_size()
ValueError: bad file descriptor

FYI, the size of the terminal associated with the C's stdout isn't related to the IDLE shell. For example, in Linux when I run IDLE from the GUI, the associated terminal size is 0x0. 

On Windows, os.get_terminal_size uses the console API GetConsoleScreenBufferInfo. This can't work given IDLE has no attached console. Also, for a GUI app the Windows C runtime leaves the standard FILE streams uninitialized to an invalid file descriptor (-1), so Python's sys.__stdout__ is None. That's why you get an AttributeError complaining that NoneType (i.e. type(None)) has no attribute 'fileno'.

Currently shutil.get_terminal_size returns the fallback size when os.get_terminal_size(sys.__stdout__.fileno()) raises NameError or OSError. I think AttributeError and ValueError should be added to this list.

I guess users need to check standard streams for None. There's not many uses of stream attributes in core libs.

Maybe catch should be Exception -- since it's documented to return a fallback on error.

I think checking for None would be better.  Catching Exception might mask other errors that the user would want to know about.

If one starts IDLE from a command-line console (python -m idlelib) or Python console (import idlelib.idle), sys.__stdout__ is the TextIOWraper for that console and .fileno() returns 1.  .get_terminal_size() will then return the console size.  The exception occurs when IDLE is  started from an icon.

Implementing David's suggestion for shutil will be easy: insert just before the fileno call
    if not sys.__stdout__: raise ValueError()
This is what os.get_terminal_size() raises on IDLE.  Comments in the code in posixpath.c make it clear that this is intended guis and the low_level os function.

This came up today on Stackoverflow when someone tried to use matplotlib.pyplot, which calls os.get_terminal_size, on IDLE.
https://stackoverflow.com/questions/46921087/pyplot-with-idle
(Patching shutil will not help for the os call.)

This issue already is fixed in 3.5 (see issue26801). The Stackoverflow question is related to 3.4 which is too old for getting this fix.

I'm wondering if it is worth to patch shutil.get_terminal_size() in IDLE so that it will return the size of PyShell output window (in characters).

If one starts IDLE from a command-line console (python -m idlelib) or Python console (import idlelib.idle), sys.__stdout__ is the TextIOWraper for that console and .fileno() returns 1.  .get_terminal_size() will then return the console size.  The exception occurs when IDLE is  started from an icon.

Implementing David's suggestion for shutil will be easy: insert just before the fileno call
    if not sys.__stdout__: raise ValueError()
This is what os.get_terminal_size() raises on IDLE.  Comments in the code in posixpath.c make it clear that this is intended guis and the low_level os function.

This came up today on Stackoverflow when someone tried to use matplotlib.pyplot, which calls os.get_terminal_size, on IDLE.
https://stackoverflow.com/questions/46921087/pyplot-with-idle
(Patching shutil will not help for the os call.)

What do you want to do Terry?

Patching shutil will help for pandas.

I am preparing a PR for shutil.get_window_size.  Pyplot should probably call that instead of the os version.

I think it is better to open a new issue for a new feature. The bug reported in this issue two years ago already is fixed.

Uh, sorry for the noise. I see now that shutil was already patched by Victor and you in #26801, so that it already works with IDLE started from an icon.  So now I don't understand your last comment, "Patching shutil will help for pandas."

stage: test needed -> resolved

stage: resolved -> test needed

superseder: Fix shutil.get_terminal_size() to catch AttributeError

nosy: + serhiy.storchaka
messages: + msg305034
resolution: out of date
stage: test needed -> resolved

messages: + msg305018

type: crash -> behavior
stage: test needed

messages: + msg249040

components: + Windows, - IDLE