Python for Data Analysis, 2nd Edition

Appendix B. More on the IPython System

In Chapter 2 we looked at the basics of using the IPython shell and Jupyter notebook. In this chapter, we explore some deeper functionality in the IPython system that can either be used from the console or within Jupyter.

B.1 Using the Command History

IPython maintains a small on-disk database containing the text of each command that you execute. This serves various purposes:

• Searching, completing, and executing previously executed commands with minimal typing

• Persisting the command history between sessions

• Logging the input/output history to a file

These features are more useful in the shell than in the notebook, since the notebook by design keeps a log of the input and output in each code cell.

Searching and Reusing the Command History

The IPython shell lets you search and execute previous code or other commands. This is useful, as you may often find yourself repeating the same commands, such as a %run command or some other code snippet. Suppose you had run:

In[7]: %run first/second/third/data_script.py

and then explored the results of the script (assuming it ran successfully) only to find that you made an incorrect calculation. After figuring out the problem and modifying data_script.py, you can start typing a few letters of the %run command and then press either the Ctrl-P key combination or the up arrow key. This will search the command history for the first prior command matching the letters you typed. Pressing either Ctrl-P or the up arrow key ...