python windows anaconda jupyter qtconsole

how to launch recent Jupyter QtConsole on Windows without a console window

This older question appears to be out of date.

It used to be (based on reading git repos and the qtconsole issue tracker) you could launch the Jupyter QtConsole without a console window running the background with:

pythonw -m jupyter qtconsole

However, in recent versions of Jupyter, this still launches the background console window.

I am wondering if anyone knows how to launch the QtConsole without the annoying console window. I know you can do this from the Anaconda Navigator program, but I don't want to launch one program so that I can then launch another program. I would prefer to have a simple batch script or even a python script so that I can launch with a Start Menu shortcut

Running the module directly also does not work:

pythonw -c "from qtconsole.qtconsoleapp import main; main()"

This still launches a new console window as in the picture, so I don't really know if this is possible in some straightforward way, or if the Anaconda Navigator is doing some black magic to make this happen

Solution

There are two problems here:

%CONDA_PREFIX%\Scripts\jupyter-qtconsole.exe marked as console executable (Subsystem field in PE optional header)
the -m ipykernel_launcher <etc> subprocess started with python.exe even if the launcher was started with pythonw.
- This one I was able to track to %CONDA_PREFIX%\share\jupyter\kernels\python3\kernel.json. It uses a full path to the executable thus doesn't trigger the logic in jupyter_client\manager.py that replaces certain patterns with sys.executable.

Both of these are specific to Anaconda and do not happen with the stock Python. As such, file a bug against https://github.com/conda-forge/qtconsole-feedstock to get this fixed.

These are the workarounds:

For the first bug, run pythonw <Scripts_dir>\jupyter-qtconsole-script.py which is the script that the .exe wraps.
(This is Anaconda-specific. Regular Python uses a different wrapping mechanism. Anaconda must be patching setuptools or something.)
For the second one, replace the full path in the aforementioned kernel.json with "python". This change will be overwritten when you update the ipykernel package that this file belongs to (this can be checked by searching for it in %CONDA_PREFIX%\pkgs).

The OP reports that this solution may break other Anaconda packages. I believe those that break make assumptions about the availability of standard streams. Though it too counts as a bug in my book, it must be coming from the fact that Anaconda packages aren't tested with this setup.

To create a shortcut/batch file to run the above command in Anaconda Prompt environment, see e.g. How to make batch files run in anaconda prompt.