docs/source/whatsnew/development.txt

=====================
 Development version
=====================

This document describes in-flight development work.

The CodeMirror js library has been updated fron 2.23 to 2.32 
this might induce a few changes in behavior of keymaps in the notebook, 
especially intenting/deindenting blocks that is now bound to Ctrl+] and ctr+[

* Exception types can now be displayed with a custom traceback, by defining a
  ``_render_traceback_()`` method which returns a list of strings, each
  containing one line of the traceback.
* A new command, ``ipython history trim`` can be used to delete everything but
  the last 1000 entries in the history database.
* The input transformation framework has been reworked. This fixes some corner
  cases, and adds more flexibility for projects which use IPython, like SymPy &
  SAGE. For more details, see :doc:`/config/inputtransforms`.


In-process kernels
------------------

The Python-language frontends, particularly the Qt console, may now communicate
with in-process kernels, in addition to the traditional out-of-process
kernels. An in-process kernel permits direct access to the kernel namespace,
which is necessary in some applications. It should be understood, however, that
the in-process kernel is not robust to bad user input and will block the main
(GUI) thread while executing. Developers must decide on a case-by-case basis
whether this tradeoff is appropriate for their application.

Backwards incompatible changes
------------------------------

* Calling :meth:`InteractiveShell.prefilter` will no longer perform static
  transformations - the processing of escaped commands such as ``%magic`` and
  ``!system``, and stripping input prompts from code blocks. This functionality
  was duplicated in :mod:`IPython.core.inputsplitter`, and the latter version
  was already what IPython relied on. A new API to transform input will be ready
  before release.
* Functions from :mod:`IPython.lib.inputhook` to control integration with GUI
  event loops are no longer exposed in the top level of :mod:`IPython.lib`.
  Code calling these should make sure to import them from
  :mod:`IPython.lib.inputhook`.
* For all kernel managers, the ``sub_channel`` attribute has been renamed to
  ``iopub_channel``.
* Users on Python versions before 2.6.6, 2.7.1 or 3.2 will now need to call
  :func:`IPython.utils.doctestreload.doctest_reload` to make doctests run 
  correctly inside IPython. Python releases since those versions are unaffected.
  For details, see :ghpull:`3068` and `Python issue 8048 <http://bugs.python.org/issue8048>`_.
* The ``InteractiveShell.cache_main_mod()`` method has been removed, and
  :meth:`~IPython.core.interactiveshell.InteractiveShell.new_main_mod` has a
  different signature, expecting a filename where earlier versions expected
  a namespace. See :ghpull:`3555` for details.