Saturday, November 30, 2013

Review of Tkinter GUI Application Development Hotshot

Here's my Amazon review of a new book on Tkinter.
Good big picture view of Tkinter, some problems in details, overly Windows specific
Packt provided me a complimentary ebook copy of the book for review purposes. This was in response to some concerns I had about whether the book was overly focused on Windows; I’ll address that below as a part of my review.
Tkinter GUI Application Development Hotshot is an introduction to Tkinter, requiring no previous experience with Tkinter but some experience with Python. The book is structured as a series of projects, nominally with each chapter being a distinct project. The first chapter is actually a collection of small examples showing how key elements of Tkinter work, chapters 2 through 6 each describe a separate application in detail, and chapter 7 describes several smaller applications more briefly. There are two appendices as well, the first of which (“Miscellaneous Tips”) pretty clearly should have been the final chapter of the book; the conclusion of the book is actually in this appendix. The second appendix constitutes a short Tkinter reference. Support code for the projects can be downloaded from Packt, and really must be downloaded, as the programs are wisely not presented in full in the book for each change to the application.
The approach of the book is to give a big picture view of Tkinter in the first chapter, describing its structure of widgets, geometry management, events and callbacks, and using Tkinter variables to provide communication between the widgets and your program. The later chapters then introduce different types of widgets and techniques for structuring GUI applications made in Tkinter. It is at this big picture level that the book seems to be strongest. The author doesn’t attempt to be encyclopedic, so there was a suitable focus on the relevant ideas, rather than details that can be checked in reference material. 
Turning to more specifics, flaws become apparent in the book. Despite a generally clear text, there are several points where formatting problems or lack of clarity cause confusion. A particularly unfortunate example of this is found in the discussion of callbacks in the first chapter: due apparently to incorrect indentation, the example of how to define a callback is nonsensical. It’s followed by mention of using lambda functions to deal with callbacks that take arguments, but the syntax given for lambda functions is wrong. There are several other instances in the text where general examples have misleading or flatly incorrect presentations, sometimes in quite important sections, such as the description of the general form of widget instantiation (chapter 1) and the specification of tags to be used with indexing in the Text widget (chapter 2). I don’t think experienced Python programmers would have much trouble with any of these, but beginners might. 
One of the strengths of Tkinter is that it is cross-platform, portable across operating systems. The author note this strength, but develops everything on Windows 7, claiming that “since Tkinter is truly cross-platform, you can follow along on Mac or Linux distributions without any modifications to our code.” As Tkinter’s cross-platform nature is an important part of why I’m considering using it, I decided to test the claim by working along exclusively on my Mac while using the same Python and Tcl/Tk versions as the author.  
The claim is flatly untrue. 
Most of the projects have visual issues, and several don’t work correctly. Buttons resize differently, so example of the pack geometry manager is rather confusing, and there isn’t a clear discussion of how it works outside this example. The text editor in the second chapter just has display issues, but these include such things as wrapped lines leading to hidden characters and the line numbering being incorrectly sized so that the lines are, effectively, numbered wrong. A short sample program in the second chapter tries to illustrate how different types of top-level windows should behave, but their described behavior isn’t observed. Mouse buttons numbering and appropriate modifier keys for keyboard shortcuts are platform specific, but without any discussion of this in the book. 
The third chapter (which is available as a sample on the Packt site), presenting a drum machine application, is a complete disaster. It depends on a third-party module called pymedia. This appears to be dead, not having been updated since 2006. It is claimed to work with Windows and Linux, but not Mac OS X or other Unix systems. It’s not in Homebrew. Searching for build information is not promising. Trying to build it doesn’t work. Just considering the interface isn’t much better. The author uses an array of buttons to set the drum patterns, registering button presses to manually set the states of the beats in the pattern. With the Mac versions of the widgets, the author’s code doesn’t correctly color the buttons to show the pattern, so you can neither see nor hear the pattern. And this because the author fakes a widget with two states using buttons, rather than using a checkbox which actually has two states. 
The chess program in chapter 4 seems to work fine. The audio player in chapter 5 does not, raising a type error in a division. This uses pyglet to actually play the audio files, but a function that needs to return a number instead returns None. Whether this is due to a platform dependency or due to a difference in the pyglet version I installed (with pip) compared to the unspecified version the author used, I do not know (and by this point in the book, was not inclined to try to figure it out). The drawing program in chapter 6 seems to work, more or less. I didn’t try the applications in chapter 7.
The author seems to have taken the approach that if it works on his system, it must be right. But it isn’t right if you take cross-platform function as part of working right, and platform dependence is only addressed in the most cursory of fashions.
Overall, the value of the book seems likely to depend strongly on the systems you want to work on. I’d probably give the book 4 out of 5 stars if you just care about Windows, and maybe 2 stars if you want to produce something cross platform. So I’ll give it three stars overall: a useful overview of Tkinter that fails to adequately treat an important use case. I have not tried the programs on Linux; I’d advised Linux users to try out the sample code and compare the results to what previews are available. 

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