ANN Leo 4.3-a3 Outlining IDE

Edward K. Ream edreamleo at
Fri Feb 25 13:45:10 CET 2005

Leo 4.3 alpha 3 is now available at

Leo 4.3 is the culmination of more than five months of work. This alpha 3
release corrects various bugs in Leo's core and in plugins. This is the
first release that include an installer for MacOSX.

The defining features of Leo 4.3:
1. Leo now stores options in @settings trees, that is, outlines whose
headline is '@settings'. When opening a .leo file, Leo looks for
@settings trees not only in the outline being opened but also in
various leoSettings.leo files.

Users can create arbitrarily complex user options with @settings
trees. Leo settings outlines are, in fact, infinitely more flexible
and powerful than any scheme based on flat text. Readers of Python's
configParser shootout take note.

2. The Preferences command temporarily replaces the outline pane with
an outline showing all the @settings trees in effect. The Preferences
command also replaces the body pane with a "settings pane". This
settings pane allows you to change the settings selected in the
outline pane using standard gui widgets.

3. Leo's read/write code in has been rewritten to support
user-defined tangling and untangling. This is a major cleanup of
Leo's core.

4. Leo now boasts an excellent Plugins Manager plugin. This plugin
enables and disables plugins automatically and tells you everything
you need to know about each plugin. This plugin also lets you download
plugins from Leo's cvs site.

5. You can install third-party extensions in Leo's extensions
directory. Leo will attempt to import such extensions from the
extensions directory when normal imports fail. The distribution contains
Python Mega Widgets in the extensions directory.

What people are saying about Leo
"[Leo] should either replace or greatly augment the development tools
that I use." -- Zak Greant

"Leo is a marriage of outlining and literate programming. Pure genius.
The main reason I am impressed with this tool is that it doesn't
affect your choice of tools. You can use whatever IDE for whatever
language and switch back and forth between Leo and it." -- Austin

"Leo is the best IDE that I have had the pleasure to use. I have been
using it now for about 2--3 months. It has totally changed not only
the way that I program, but also the way that I store and organize all
of the information that I need for the job that I do." -- Ian Mulvany

"I only have one week of Leo experience but I already know it will be
my default IDE/project manager...people complain about the lack of a
project manager for the free/standard Python IDE's like Idle. Leo
clearly solves that problem and in a way that commercial tools can't
touch." -- Marshall Parsons

"[Leo has] become my main development platform, and I do this for a
living. -- Nicola Larosa

"I have been using Leo for about 3 weeks and I hardly use my other
programming editor anymore...I find it easy and enjoyable to use. I
plan to adopt it as my presentation tool for code reviews." -- Jim

"I'm absolutely astounded by the power of such a simple idea! It works
great and I can immediately see the benefits of using Leo in place of
the standard flat file editor." -- Tom Lee, <tomlee at>

I think you're really showing what open source can do and your current
trajectory puts you on track to kick Emacs into the dustbin of
computing history. -- Dan Winkler

More quotes at:

What makes Leo special?
- Leo's outlines add a new dimension to programming.
- Leo shows you your code and data the way _you_ want to see them.
- Leo extends, completes and simplifies literate programming.
- Leo's script buttons bring scripts to data.

What is Leo?
- A programmer's editor, an outlining editor and a flexible browser.
- A literate programming tool, compatible with noweb and CWEB.
- A data organizer and project manager. Leo provides multiple views
   of projects within a single outline.
- Fully scriptable using Python. Leo saves its files in XML format.
- Portable. is 100% pure Python.
- Open Software, distributed under the Python License.

Leo requires Python 2.2.1 or above and tcl/tk 8.4 or above.
Leo works on Linux, Windows and MacOs X.


Edward K. Ream
Edward K. Ream   email:  edreamleo at
Leo: Literate Editor with Outlines

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