Why Use IPython?

IPython gives you quite a lot of functionality lacking in the standard Python shell. The benefits of installing and using IPython as your shell are numerous. Its features include:

• Easy-to-read documentation hooks

• Autocompletion and magic commands for library, class, and object exploration

• Inline image and chart generation

• Helpful tools to view history, create files, debug your script, reload your script, and more

• Built-in shell command usage

• Auto-imports on startup

It’s also one of the core components of Jupyter, a shared notebook server allowing for rapid-cycle data exploration in a browser. We covered using Jupyter for code sharing and presentation in Chapter 10.

Getting Started with IPython

IPython is easy to install with pip:

pip install ipython

If you are using more than one virtual environment, you might want to install IPython globally or within each virtual environment. To begin using IPython, simply type ipython in your terminal window. You should see a prompt similar to this:

$ ipython
Python 2.7.6 (default, Mar 22 2014, 22:59:56)
Type "copyright", "credits" or "license" for more information.

IPython 1.2.1 -- 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]:

You can now type Python commands as you would in a normal Python shell. For example:

In [1]: 1 + 1
Out[1]: 2

In [2]: from datetime import datetime

In [3]: datetime.now()
Out[3]: datetime.datetime(2015, 9, 13, 11, 47, 49, 191842)

When you need to exit the shell, you can type quit(), exit(), or Ctrl-D on Windows/Linux or Cmd-D on Mac.

Magic Functions

IPython has numerous so-called magic functions to help you as you explore and program. Here are some of the most useful ones, especially for beginning developers.

To easily see everything you have imported and all active objects, you can type %whos or %who. Let’s take a look at their usage:

In [1]: foo = 1 + 4

In [2]: bar = [1, 2, 4, 6]

In [3]: from datetime import datetime

In [4]: baz = datetime.now()

In [5]: %who
bar baz datetime    foo

In [6]: %whos
Variable   Type        Data/Info
--------------------------------
bar        list        n=4
baz        datetime    2015-09-13 11:53:29.282405
datetime   type        <type 'datetime.datetime'>
foo        int         5

This can be incredibly helpful if you have forgotten a variable name or want to see what you have stored in your variables in one concise list.

Another useful tool is the ability to quickly look up documentation related to libraries, classes, or objects. If you type a ? at the end of the name of the method, class, library, or attribute, IPython will attempt to retrieve any related documentation and display it inline. For example:

In [7]: datetime.today?
Type:       builtin_function_or_method
String Form:<built-in method today of type object at 0x7f95674e0a00>
Docstring:  Current date or datetime:
            same as self.__class__.fromtimestamp(time.time()).

There are tons of IPython extensions and functions similar to these that are tremendously useful for development, particularly as you grow as a developer and encounter more complicated issues. Table F-1 lists some of the most useful ones, but there are also some great presentations and conference talks and interactive examples available online, as well as the library’s well-written documentation.

There are many more magic commands available. Their usefulness will depend on what you use IPython for in your development, but employing them as you grow as a developer will likely shed light on other tasks IPython can simplify for you.

Final Thoughts: A Simpler Terminal

Whether you use IPython only in a notebook or in your active terminal development, we believe it will help you write and understand Python and grow as a developer. Much of your early development will be exploring how Python works and what errors and exceptions you encounter along the way. IPython is great for these lessons, as you can try again on the next input line. We hope IPython will keep you learning and writing Python for many years to come.