For this recipe, you will need a recent IPython installation. The instructions to install IPython are at http://ipython.org/install.html (retrieved July 2015). Install it using the pip command:

$ [sudo] pip install ipython/jupyter

If you have installed IPython via Anaconda already, check for updates with the following commands:

$ conda update conda
$ conda update ipython ipython-notebook ipython-qtconsole

I have IPython 3.2.0 as part of the Anaconda distribution.

We will install log a Python session and use the watermark extension to track package versions and other information. Start an IPython shell or notebook. When we start a session, we can use the command line switch --logfile=<file name>.py. In this recipe, we use the %logstart magic (IPython terminology) function:

In [1]: %logstart cookbook_log.py rotate
Activating auto-logging. Current session state plus future input saved.
Filename       : cookbook_log.py
Mode           : rotate
Output logging : False
Raw input log  : False
Timestamping   : False
State          : active

This example invocation started logging to a file in rotate mode. Both the filename and mode are optional. Turn logging off and back on again as follows:

In [2]: %logoff
Switching logging OFF

In [3]: %logon
Switching logging ON

Install the watermark magic from Github with the following command:

In [4]: %install_ext https://raw.githubusercontent.com/rasbt/watermark/master/watermark.py

The preceding line downloads a Python file, in my case, to ~/.ipython/extensions/watermark.py. Load the extension by typing the following line:

%load_ext watermark

The extension can place timestamps as well as software and hardware information. Get additional usage documentation and version (I installed watermark 1.2.2) with the following command:

%watermark?

For example, call watermark without any arguments:

In [7]: %watermark
… Omitting time stamp …

CPython 3.4.3
IPython 3.2.0

compiler   : Omitting
system     : Omitting
release    : 14.3.0
machine    : x86_64
processor  : i386
CPU cores  : 8
interpreter: 64bit

I omitted the timestamp and other information for personal reasons. A more complete example follows with author name (-a), versions of packages specified as a comma-separated string (-p), and custom time (-c) in a strftime() based format:

In [8]: %watermark -a "Ivan Idris" -v -p numpy,scipy,matplotlib -c '%b %Y' -w
Ivan Idris 'Jul 2015'

CPython 3.4.3
IPython 3.2.0

numpy 1.9.2
scipy 0.15.1
matplotlib 1.4.3
watermark v. 1.2.2

The IPython logger writes commands you type to a Python file. Most of the lines are in the following format:

get_ipython().magic('STRING_YOU_TYPED')

You can replay the session with %load <log file>. The logging modes are described in the following table:

We used a custom magic function available on the Internet. The code for the function is in a single Python file and it should be easy for you to follow. If you want different behavior, you just need to modify the file.