qtconsole + _repr_html_ bug

[csakhil]

Printing a pandas.DataFrame in IPython's qtconsole tries to use _repr_html_. This method returns None if the terminal window that started the IPython session is too small.

I'm not sure this behaviour is right. When you're in the qtconsole, _repr_html_ should check the size of the qtconsole window and not the the size of the terminal that started the session.

Here are some steps to reproduce the issue:

1. Create a very small terminal window and run ipython qtconsole.
2. Create a pandas.DataFrame called df.
3. Run df.head() in IPython. You should notice that the HTML representation of the table is not used.
4. Maximize the small terminal window from step 1.
5. Run df.head() in IPython. The HTML representation is now used.

I would guess the easiest way to fix this would be to add a qtconsole "os" in get_terminal_size in util/terminal.py and use Qt hooks to figure out the dimensions of the qtconsole.

[lodagro]

Besides the qtconsole this is also the case in the ipython notebook (i thought there was an issue about this one too, but can`t find it). Idle #1714, has a similar problem.

Sounds like you have a solution for the qtconsole, can you elaborate? I added the get_terminal_size code, but i`m unfamiliar with Qt.

IPython zmq front ends run in a seperate process from the kernel, and I couldn't locate any interface for
querying the front end for things like geometry.

Though, It's possible to detect whether the code is running under IPython and under what specific front-end.

[csakhil]

The easiest solution might be to always use the HTML representation if within a qtconsole or IPython notebook.

[lodagro]

Reason not always _repr_html_ is used, is to handle large frames (see also discussion in #772).
Maybe we could bypass auto detect of terminal size in qtconsole, and use hard coded values for max columns/rows (html has scrollable divs)? And if the frame is too big (it would take too long to render) switch over to summary view.

For reference also mentioning #829 (no means to get ipython notbook size).

[changhiskhan]

What's the best way to test whether the code is running under terminal or some graphical frontend? just check whether get_ipython returns ZMQInteractiveShell?

yes, And:

get_ipython().config['KernelApp']['parent_appname']

gets you the specific front-end since at least 0.12 I believe.

[changhiskhan]

hmmm...how do you test this?

inject into globals()/context manager?

[changhiskhan]

yeah, can't think of anything better.
I'll just have to make a fake get_ipython function etc.
Thanks!

you could also wrap get_ipython inside something in common, and invoke that
rather then get_ipython directly, then add some testing hooks to set the return value.
cleaner, but perhaps overkill.

[changhiskhan]

probably fine for now.

[wesm]

In addition to Chang's PR, I disabled HTML output altogether until there's a way to get the window size in characters