After a kernel reset, input line hangs about qtconsole

[ccordoba12]

What's you Matplotlib backend?

[dashesy]

It is Qt4Agg

[ccordoba12]

Please disable one of your startup magics, and then the other, to
determine which one is causing this problem.

Sorry for not being more helpful, but I haven't seen this problem before.

El 17/12/15 a las 12:14, Ehsan Azar escribió:

It is |Qt4Agg|

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#76 (comment).

[dashesy]

It seems sometimes the std output of the startup magic leaks into the input stream after reboot.

When I hit enter when input hangs I got this:

NameError: name 'atplotlib' is not defined

Which is result of trying to execute the console output of:

Using matplotlib backend: Qt4Agg

[dashesy]

Here is the log file when input hangs:

[JupyterQtConsoleApp] WARNING | kernel restarted
[JupyterQtConsoleApp] execute_input: {u'execution_count': 1, u'code': u'\n\n\n\n'}
[JupyterQtConsoleApp] execute: {u'status': u'ok', u'execution_count': 0, u'user_expressions': {}, u'payload': []}
QTextCursor::setPosition: Position '80967' out of range
QTextCursor::setPosition: Position '80967' out of range
QTextCursor::setPosition: Position '80967' out of range
QTextCursor::setPosition: Position '80967' out of range
[JupyterQtConsoleApp] execute_input: {u'execution_count': 1, u'code': u'\n'}
[JupyterQtConsoleApp] execute: {u'status': u'ok', u'execution_count': 0, u'user_expressions': {}, u'payload': []}
[JupyterQtConsoleApp] Starting kernel: ['/home/dashesy/.virtualenvs/qtconsole/bin/python', '-m', 'ipykernel', '-f', u'/run/user/1000/jupyter/kernel-3011.json']
[JupyterQtConsoleApp] Connecting to: tcp://127.0.0.1:44711
QTextCursor::setPosition: Position '29967' out of range
[JupyterQtConsoleApp] shutdown: {u'status': u'ok', u'restart': True}
[JupyterQtConsoleApp] stream: {u'text': u'Using matplotlib backend: TkAgg\nPopulating the interactive namespace from numpy and matplotlib\n', u'name': u'stdout'}
QTextCursor::setPosition: Position '29993' out of range

1. Every time it hangs I see QTextCursor::setPosition after the line about stream

2. Only Enter is hanged, I can type:

   a. either I have to type a very long character string for buffer to be ready again
   b. or I can use Backspace! which deletes the line Populating the interactive namespace from numpy and matplotlib but then I can press Enter again

It is reproducible too. I use this script it generates lots of QTextCursor::setPosition messages, then I restart the kernel (usually twice) fast. This sounds contrived but has the effect of reproducing the error.

[dashesy]

Ok it is this line that results in QTextCursor::setPosition warnings:

cursor.setPosition(self._append_before_prompt_pos)

Why it sometimes coincides with in input stream hanging I will try to figure out now

[dashesy]

Another way to reproduce input hang, without restarting the kernel:

1. Run this script for little while
2. Run np? then hit q
3. Try Enter key or arrows, and the input hangs and terminal will have lots of QTextCursor::setPosition: Position 'X' out of range
   warnings

[takluyver]

We've had recurring problems with those 'Position xyz out of range' warnings followed by input hanging.