Hello, 

I found a wrong behavior with IPython 4 in combination with Python 3.5.1. 

Normally in a command like "In [2]: !echo {a}" everything inside {} is interpreted with python and inserted to executed the line with bash. After I done a upgrade tp Python 3.5.1 this wasn't working. After a downgrade (3.5.0) it was working.

In the bottom is an example, where "In [2]: !echo {a}" are the important lines.
In [2]: !echo {a}
 * Python 3.5.0 -> 3
 * Python 3.5.1 -> {a}

Best regards
Christoph 

-----------------------------------------------------------------------
$ ipython
Python 3.5.1 |Anaconda 2.4.0 (64-bit)| (default, Dec  7 2015, 11:16:01) 
Type "copyright", "credits" or "license" for more information.

IPython 4.0.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: a = 3

In [2]: !echo {a}
{a}

In [3]: 
-----------------------------------------------------------------------
conda install python=3.5.0
Fetching package metadata: ....
Solving package specifications: ................
Package plan for installation in environment /opt/anaconda3:

The following packages will be DOWNGRADED:

    python: 3.5.1-0 --> 3.5.0-1

Proceed ([y]/n)? y

Unlinking packages ...
[      COMPLETE      ]|###################################################| 100%
Linking packages ...
[      COMPLETE      ]|###################################################| 100%

-----------------------------------------------------------------------

$ ipython
Python 3.5.0 |Anaconda 2.4.0 (64-bit)| (default, Oct 19 2015, 21:57:25) 
Type "copyright", "credits" or "license" for more information.

IPython 4.0.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: a = 3

In [2]: !echo {a}
3

In [3]: