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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 plus SQ/ICADD Tables//EN" "html.dtd"
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<HTML><HEAD><TITLE>Wpy, a Portable GUI Module for Python</TITLE></HEAD>
<BODY><H2>Wpy, a Portable GUI Module for Python</H2> <STRONG>Presented
at the May 1995 Python Workshop by <A HREF="mailto:jim@interet.com">James
C. Ahlstrom</A>
</STRONG><P>Wpy is a Python module which provides a class library, a
message system and other tools for writing portable graphical user
interface (GUI) code. You import "wpy.py" into your Python program and
use it to write GUI code which will run unchanged on Unix/X using Tk, or
on Microsoft Windows 3.1 and NT. Python is ideally suited to GUI
development since it is a fast object-oriented scripting language with
advanced data types such as lists and dictionaries. Code written with
wpy runs with native look and feel. </P><P> When running on Unix/X, wpy
uses Tk to provide a high level interface to the X window system. The
newest version of Tk (currently 4.0 beta 3) is required. Interface code
to Tk is provided in the file "wpy_tk.py". When running on Microsoft
Windows 95 or NT, the interface is provided by a C++ language module.
The Windows version will also run on Windows 3.1 using a free "win32s"
dynamic link library provided by Microsoft. </P><P> All the wpy source
and binary versions are available from <A HREF="ftp://ftp.interet.com/pub/python/"
>ftp.interet.com</A> in /pub/python. This may be moved to <A HREF="http://www.python.org/"
>www.python.org
</A>in the future. The software is free but carries no warranty. See
the copyright notice. The software is currently (May 1995) somewhat
preliminary, and is still under active development. </P>
<H2>Design Goals </H2>The best way to understand wpy is to look at the
design goals which are as follows: <UL>
<LI>Must support native look and feel on Unix/X and Windows, and
hopefully the Macintosh and OS/2 </LI>
<LI>Must have a strongly object-oriented design and use inheritance
</LI>
<LI>Should provide a high-level interface, and be easy to use </LI>
<LI>Should be a thin layer on all platforms, and be small and simple
</LI>
<LI>Must look natural and native to Python, and take advantage of
Python language features </LI>
<LI>Must support at least "medium" and preferably "large" GUI programs
with industrial-strength robustness </LI>
<LI> Some advanced GUI features and commercial elegance may be
sacrificed for portability and simplicity</LI></UL> <H2>Wpy Design
</H2> <P>Wpy has its own GUI class model. In view of the effort
required to learn any GUI model, inventing a new model is not desirable.
Instead, I attempted to identify a good popular class model which would
be worthwhile to learn even apart from its use in wpy. In the end, the
obvious choice was the Microsoft Foundation Class (MFC) model. Wpy
follows MFC rather exactly in its classes and messages, but differs
slightly in details such as method arguments. A knowledge of MFC makes
writing in wpy easy and obvious, and even MFC documentation can be used
for wpy. The reverse is also true, and wpy is a good way to learn MFC.
The Python/wpy code looks more or less identical to the equivalent C++
version, but is faster and easier to write. </P><P> Wpy is being
developed as a commercial quality language, but I believe that Python
and wpy are also an excellent choice for a teaching language. The
skills learned will translate directly to C++ without the risk of
writing C and calling it C++. </P><P>MFC is a natural choice when
running under Windows, and it is easy to see how a port would work. On
Unix, the Tk interface is used. Tk is a command language interface to X
widgets, and it is not a direct map to MFC or any other class library.
Luckily Tk provides powerful commands which make it easy to implement
high level features easily. In wpy, the Tk internals are hidden, and
the GUI model is still MFC. Necessary support is provided in Python
code which calls Tk commands through the tkinter module provided in
standard Python. </P><H2>Wpy Status </H2> <P>The feature set of wpy
and the documentation will improve now that the design is complete.
Currently (May 1995) only a few types of controls are implemented and
even these could use more testing. Wpy only recently graduated from the
"proof of concept" stage to the "in development" stage. So far, results
are promising. I hope that wpy will be a useful addition to the already
great Python language.
</P><P><A HREF="mailto:jim@interet.com">James C. Ahlstrom</A> <BR>May
30, 1995</P></BODY>
</HTML>
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