A Comprehensive Introduction to Python Programming and ... - MSDL

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2 Python and Tkinter for RAD and Prototyping 2.1 Designing User Interfaces User interfaces are what allows end users to interact with an application. An application can be excellent, but without a good user interface, it becomes more difficult to use, and less enjoyable. It is thus very important to design good user interfaces. Designing user interface takes place at two different levels: the graphical level and the event level. Graphical elements of a user interface are called widgets. Widgets are basic components like buttons, scrollbars, etc. But user interfaces involve more than a collection of widgets placed in a window. The application must be able to respond to mouse clicks, keyboard actions or system events such as minimizing the window. For this to happen, events must be associated to some pieces of code. This process is called binding. The next two chapters will cover each level in more details, but this chapter will present an overview of Tkinter and explain why it has become the leading GUI toolkit for the Python language. 2.2 What is Tkinter? Tkinter is an open source, portable graphical user interface (GUI) library designed for use in Python scripts. Tkinter relies on the Tk library, the GUI library used by Tcl/Tk and Perl, which is in turn implemented in C. Thus, Tkinter is implemented using multiple layers. Several competing GUI toolkits are available to use with the Python language, namely:
2.3 Why Tkinter? 18 / 75 wxPython : a wrapper extension for wxWindows, a portable GUI library originally developed for the C++ language. It is the second most popular GUI toolkit for Python since it is considered excellent for complex interface design. JPython (Jython) : since it is implemented in java, JPython has access to Java GUI libraries, namely SWING and AWT. Recently, JTkinter has been implemented and provides a Tkinter port to JPython using the Java Native Interface (JNI). PyKDE / PyQt, PyGTK : these packages provide an access to KDE and Gnome GUI libraries to python scripts. Win32all.exe : provides access to Microsoft Foundation Classes (MFC) to python scripts. It is limited to run on MS Windows only. WPY : a GUI library that can be used on both Microsoft Windows and UNIX X Windows. This library uses the MFC coding style. X11 : a library based on the X Windows and Motif libraries allowing excellent control of the X11 environment, but are limited to run on X Windows OS’s only. 2.3 Why Tkinter? With all the competing GUI toolkits available for the Python language, what makes Tkinter stand out of the rest? Why is it the most popular toolkit for use interface design? To find the answer, one must look at the advantages that it offers. 1. Layered design The layered approach used in designing Tkinter gives Tkinter all of the advantages of the TK library. Therefore, at the time of creation, Tkinter inherited from the benefits of a GUI toolkit that had been given time to mature. This makes early versions of Tkinter a lot more stable and reliable than if it had been rewritten from scratch. Moreover, the conversion from Tcl/Tk to Tkinter is really trivial, so that Tk programmers can learn to use Tkinter very easily. 2. Accessibility Learning Tkinter is very intuitive, and therefore quick and painless. The Tkinter implementation hides the detailed and complicated calls in simple, intuitive methods. This is a continuation of the Python way of thinking, since the language excels at quickly building prototypes. It is therefore expected that its preferred GUI library be implemented using the same approach. For example, here is the code for a typical “Hello world”-like application: Listing 19: A Simple Application from Tkinter import * root = Tk( ) root.title(’A simple application’) root.mainloop( )
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