Color

The default IPython configuration has most bells and whistles turned on (they're pretty safe). But there's one that may cause problems on some systems: the use of color on screen for displaying information. This is very useful, since IPython can show prompts and exception tracebacks with various colors, display syntax-highlighted source code, and in general make it easier to visually parse information.

The following terminals seem to handle the color sequences fine:

• Linux main text console, KDE Konsole, Gnome Terminal, E-term, rxvt, xterm.
• CDE terminal (tested under Solaris). This one boldfaces light colors.
• (X)Emacs buffers. See the :ref:`emacs` section for more details on using IPython with (X)Emacs.
• A Windows (XP/2k) command prompt with pyreadline.
• A Windows (XP/2k) CygWin shell. Although some users have reported problems; it is not clear whether there is an issue for everyone or only under specific configurations. If you have full color support under cygwin, please post to the IPython mailing list so this issue can be resolved for all users.

These have shown problems:

• Windows command prompt in WinXP/2k logged into a Linux machine via telnet or ssh.
• Windows native command prompt in WinXP/2k, without Gary Bishop's extensions. Once Gary's readline library is installed, the normal WinXP/2k command prompt works perfectly.

Currently the following color schemes are available:

• NoColor: uses no color escapes at all (all escapes are empty '' '' strings). This 'scheme' is thus fully safe to use in any terminal.
• Linux: works well in Linux console type environments: dark background with light fonts. It uses bright colors for information, so it is difficult to read if you have a light colored background.
• LightBG: the basic colors are similar to those in the Linux scheme but darker. It is easy to read in terminals with light backgrounds.

IPython uses colors for two main groups of things: prompts and tracebacks which are directly printed to the terminal, and the object introspection system which passes large sets of data through a pager.

Input/Output prompts and exception tracebacks

You can test whether the colored prompts and tracebacks work on your system interactively by typing '%colors Linux' at the prompt (use '%colors LightBG' if your terminal has a light background). If the input prompt shows garbage like:

[0;32mIn [[1;32m1[0;32m]: [0;00m

instead of (in color) something like:

In [1]:

this means that your terminal doesn't properly handle color escape sequences. You can go to a 'no color' mode by typing '%colors NoColor'.

You can try using a different terminal emulator program (Emacs users, see below). To permanently set your color preferences, edit the file $IPYTHONDIR/ipythonrc and set the colors option to the desired value.

Object details (types, docstrings, source code, etc.)

IPython has a set of special functions for studying the objects you are working with, discussed in detail :ref:`here <dynamic_object_info>`. But this system relies on passing information which is longer than your screen through a data pager, such as the common Unix less and more programs. In order to be able to see this information in color, your pager needs to be properly configured. I strongly recommend using less instead of more, as it seems that more simply can not understand colored text correctly.

In order to configure less as your default pager, do the following:

1. Set the environment PAGER variable to less.
2. Set the environment LESS variable to -r (plus any other options you always want to pass to less by default). This tells less to properly interpret control sequences, which is how color information is given to your terminal.

For the bash shell, add to your ~/.bashrc file the lines:

export PAGER=less
export LESS=-r

For the csh or tcsh shells, add to your ~/.cshrc file the lines:

setenv PAGER less
setenv LESS -r

There is similar syntax for other Unix shells, look at your system documentation for details.

If you are on a system which lacks proper data pagers (such as Windows), IPython will use a very limited builtin pager.

Fine-tuning your prompt

IPython's prompts can be customized using a syntax similar to that of the bash shell. Many of bash's escapes are supported, as well as a few additional ones. We list them below:

\#
    the prompt/history count number. This escape is automatically
    wrapped in the coloring codes for the currently active color scheme.
\N
    the 'naked' prompt/history count number: this is just the number
    itself, without any coloring applied to it. This lets you produce
    numbered prompts with your own colors.
\D
    the prompt/history count, with the actual digits replaced by dots.
    Used mainly in continuation prompts (prompt_in2)
\w
    the current working directory
\W
    the basename of current working directory
\Xn
    where $n=0\ldots5.$ The current working directory, with $HOME
    replaced by ~, and filtered out to contain only $n$ path elements
\Yn
    Similar to \Xn, but with the $n+1$ element included if it is ~ (this
    is similar to the behavior of the %cn escapes in tcsh)
\u
    the username of the current user
\$
    if the effective UID is 0, a #, otherwise a $
\h
    the hostname up to the first '.'
\H
    the hostname
\n
    a newline
\r
    a carriage return
\v
    IPython version string

In addition to these, ANSI color escapes can be insterted into the prompts, as C_ColorName. The list of valid color names is: Black, Blue, Brown, Cyan, DarkGray, Green, LightBlue, LightCyan, LightGray, LightGreen, LightPurple, LightRed, NoColor, Normal, Purple, Red, White, Yellow.

Finally, IPython supports the evaluation of arbitrary expressions in your prompt string. The prompt strings are evaluated through the syntax of PEP 215, but basically you can use $x.y to expand the value of x.y, and for more complicated expressions you can use braces: ${foo()+x} will call function foo and add to it the value of x, before putting the result into your prompt. For example, using prompt_in1 '${commands.getoutput("uptime")}nIn [#]: ' will print the result of the uptime command on each prompt (assuming the commands module has been imported in your ipythonrc file).

Prompt examples

The following options in an ipythonrc file will give you IPython's default prompts:

prompt_in1 'In [\#]:'
prompt_in2 '   .\D.:'
prompt_out 'Out[\#]:'

which look like this:

In [1]: 1+2
Out[1]: 3

In [2]: for i in (1,2,3):
   ...:    print i,
   ...:
1 2 3

These will give you a very colorful prompt with path information:

#prompt_in1 '\C_Red\u\C_Blue[\C_Cyan\Y1\C_Blue]\C_LightGreen\#>'
prompt_in2 ' ..\D>'
prompt_out '<\#>'

which look like this:

fperez[~/ipython]1> 1+2
                <1> 3
fperez[~/ipython]2> for i in (1,2,3):
               ...>     print i,
               ...>
1 2 3