One of Python's most useful features is its interactive interpreter. This system allows very fast testing of ideas without the overhead of creating test files as is typical in most programming languages. However, the interpreter supplied with the standard Python distribution is somewhat limited for extended interactive use.

The May/June 2007 issue of the journal Computing in Science and Engineering was devoted to Python in scientific computing. This featured article, written by Fernando Perez and Brian Granger, describes IPython's design and main features.

You can also see what projects are using IPython, or check out the talks and presentations we have given about IPython.

This page contains links to detailed documentation.

Goals

IPython is a free software project (released under the BSD license) which tries to:

• Provide an interactive shell superior to Python's default. IPython has many features for object introspection, system shell access, and its own special command system for adding functionality when working interactively. It tries to be a very efficient environment both for Python code development and for exploration of problems using Python objects (in situations like data analysis).
• Serve as an embeddable, ready to use interpreter for your own programs. IPython can be started with a single call from inside another program, providing access to the current namespace. This can be very useful both for debugging purposes and for situations where a blend of batch-processing and interactive exploration are needed.
• Offer a flexible framework which can be used as the base environment for other systems with Python as the underlying language. Specifically scientific environments like Mathematica, IDL and Mathcad inspired its design, but similar ideas can be useful in many fields.
• Allow interactive testing of threaded graphical toolkits. IPython has support for interactive, non-blocking control of GTK, Qt and WX applications via special threading flags. The normal Python shell can only do this for Tkinter applications.

Features

• Dynamic object introspection. One can access docstrings, function definition prototypes, source code, source files and other details of any object accessible to the interpreter with a single keystroke ('?').
• Completion in the local namespace, by typing TAB at the prompt. This works for keywords, methods, variables and files in the current directory. This is supported via the readline library, and full access to configuring readline's behavior is provided.
• Numbered input/output prompts with command history (persistent across sessions and tied to each profile), full searching in this history and caching of all input and output.
• User-extensible 'magic' commands. A set of commands prefixed with % is available for controlling IPython itself and provides directory control, namespace information and many aliases to common system shell commands.
• Alias facility for defining your own system aliases.
• Complete system shell access. Lines starting with ! are passed directly to the system shell, and using !! captures shell output into python variables for further use.
• Background execution of Python commands in a separate thread. IPython has an internal job manager called jobs, and a convenience backgrounding magic function called %bg.
• The ability to expand python variables when calling the system shell. In a shell command, any python variable prefixed with $ is expanded. A double $$ allows passing a literal $ to the shell (for access to shell and environment variables like $PATH).
• Filesystem navigation, via a magic %cd command, along with a persistent bookmark system (using %bookmark) for fast access to frequently visited directories.
• Automatic indentation (optional) of code as you type (through the readline library).
• Macro system for quickly re-executing multiple lines of previous input with a single name.
• Session logging (you can then later use these logs as code in your programs).
• Session restoring: logs can be replayed to restore a previous session to the state where you left it.
• Verbose and colored exception traceback printouts. Easier to parse visually, and in verbose mode they produce a lot of useful debugging information (basically a terminal version of the cgitb module).
• Auto-parentheses: callable objects can be executed without parentheses: 'sin 3' is automatically converted to 'sin(3)'.
• Auto-quoting: using ',' as the first character forces auto-quoting of the rest of the line: 'my_function a b' automatically becomes 'my_function("a","b")'.

• Extensible input syntax. You can define filters that pre-process user input to simplify input in special situations. This allows, for example, pasting multi-line code fragments which start with '>>>' or '...' such as those from other python sessions or the standard Python documentation.

• Flexible configuration system. It uses a configuration file which allows permanent setting of all command-line options, module loading, code and file execution. The system allows recursive file inclusion, so you can have a base file with defaults and layers which load other customizations for particular projects.
• Embeddable. You can call IPython as a python shell inside your own python programs. This can be used both for debugging code or for providing interactive abilities to your programs with knowledge about the local namespaces (very useful in debugging and data analysis situations).
• Easy debugger access. You can set IPython to call up the Python debugger (pdb) every time there is an uncaught exception. This drops you inside the code which triggered the exception with all the data live and it is possible to navigate the stack to rapidly isolate the source of a bug. The %run magic command -with the -d option- can run any script under pdb's control, automatically setting initial breakpoints for you.
• Profiler support. You can run single statements (similar to profile.run()) or complete programs under the profiler's control. While this is possible with the standard profile module, IPython wraps this functionality with magic commands (see '%prun' and '%run -p') convenient for rapid interactive work.