Section 19.1. Introduction

19.1. Introduction

19.1.1. What Are Tcl, Tk, and Tkinter?

Tkinter is Python's default GUI library. It is based on the Tk toolkit, originally designed for the Tool Command Language (Tcl). Due to Tk's popularity, it has been ported to a variety of other scripting languages, including Perl (Perl/Tk), Ruby (Ruby/Tk), and Python (Tkinter). With the GUI development portability and flexibility of Tk, along with the simplicity of scripting language integrated with the power of systems language, you are given the tools to rapidly design and implement a wide variety of commercial-quality GUI applications.

If you are new to GUI programming, you will be pleasantly surprised at how easy it is. You will also find that Python, along with Tkinter, provides a fast and exciting way to build applications that are fun (and perhaps useful) and that would have taken much longer if you had had to program directly in C/C++ with the native windowing system's libraries. Once you have designed the application and the look and feel that goes along with your program, you will use basic building blocks known as widgets to piece together the desired components, and finally, to attach functionality to "make it real."

If you are an old hand at using Tk, either with Tcl or Perl, you will find Python a refreshing way to program GUIs. On top of that, it provides an even faster rapid prototyping system for building them. Remember that you also have Python's system accessibility, networking functionality, XML, numerical and visual processing, database access, and all the other standard library and third-party extension modules.

Once you get Tkinter up on your system, it will take less than 15 minutes to get your first GUI application running.

19.1.2. Getting Tkinter Installed and Working

Like threading, Tkinter is not necessarily turned on by default on your system. You can tell whether Tkinter is available for your Python interpreter by attempting to import the Tkinter module. If Tkinter is available, then no errors occur:

>>> import Tkinter >>>

If your Python interpreter was not compiled with Tkinter enabled, the module import fails:

>>> import Tkinter Traceback (innermost last):   File "<stdin>", line 1, in ?   File "/usr/lib/python1.5/lib-tk/Tkinter.py", line 8, in ?      import _tkinter # If  this fails your Python may not be configured for Tk ImportError: No module named _tkinter

You may have to recompile your Python interpreter to get access to Tkinter. This usually involves editing the Modules/Setup file and enabling all the correct settings to compile your Python interpreter with hooks to Tkinter or choosing to have Tk installed on your system. Check the README file for your Python distribution for specific instructions on getting Tkinter to compile on your system. Be sure, after your compilation, that you start the new Python interpreter you just created; otherwise, it will act just like your old one without Tkinter (and in fact, it is your old one).

19.1.3. Client/Server ArchitectureTake Two

In the earlier chapter on network programming, we introduced the notion of client/server computing. A windowing system is another example of a software server. These run on a machine with an attached display, such as a monitor of some sort. There are clients, tooprograms that require a windowing environment to execute, also known as GUI applications. Such applications cannot run without a windows system.

The architecture becomes even more interesting when networking comes into play. Usually when a GUI application is executed, it displays to the machine that it started on (via the windowing server), but it is possible in some networked windowing environments, such as the X Window system on Unix, to choose another machine's window server to display to. In such situations, you can be running a GUI program on one machine, but have it displayed on another!