Text Processing in Python [Englisch] [Taschenbuch]

If you have read an introductory book or two about programming, but you are far from being an expert, then you will benefit a lot from reading this book. If you are a competent programmer in any other language, you will benefit from this book. If you are an expert Python programmer, you will also benefit from this book.

For, as you know, there are many good introductory texts about Python. This is not one of them, for this is an advanced book, but not an inaccessible one. David Mertz has a unique style and focus that we have become familiar with from his "Charming Python" series of articles on the IBM Developer Network. Dr. Mertz is more interested in facilitating our learning process than in lecturing us, and rather than fill his pages with impressive examples designed to illustrate his expertise, he gently guides us by offering subtle yet important examples of code and analysis that makes us think for ourselves.

He has a special talent for programming in the functional style, and this is a great introduction to that style of Python programming. Thus, this is also a good guide to using the newer features introduced into Python in the last few revisions, which often facilitate the functional style of programming.

The text includes, in an appendix, a 40 page tutorial covering the basic Python language. This tutorial is, like the book, unique in its approach and is worthwhile even for experienced Pythonistas, as it sheds light on some of the underlying ideas behind the syntax and semantics, and it also illustrates the functional style of programming, which is sometimes quite useful when doing text processing. And, despite its many other virtues, this is a book about text processing.

Chapter 1 covers the Python basics, but with a particular eye towards those features most critical and useful for text processing. Chapter 2 covers the basic string operations as found in the string module and the newer built-in string functions. Chapter three is about Regular Expressions, and, although I am shy about regexes because of their relative complexity, I am very glad to have read this chapter and will no longer be intimidated when regexes are the correct approach to take! Chapter 4 is on Parsers and State machines, which are important for processing nested text, as in everyday HTML, XML and the like. This chapter is not as esoteric as its title may sound to relative newbies (like myself), as it does offer useful ideas and principles for dealing with HTML. How much more useful can a topic be than that? It is true that a deep understanding of this subject may be beyond myself and other relative duffers, but this chapter has much to offer those like me and I am sure much more to offer professionals.

Chapter 5 is on Internet tools and techniques, and this a good example of how text processing touches every important area of computer programming. We manipulate text for email, newsgroups, CGI programs, HTML and many other aspects of net programming. A good summary of XML programming is included, as well as useful synopses of other Python internet modules, from a text processing point of view.

Appendix A is the aforementioned selective and short review of Python basics. Appendix B is a ten page Data Compression primer that is quite educational. Appendix C offers the same good service for Unicode, and Appendix D covers the author's own software, a state machine for adding markup to text, which is backed up by his extensive web site that has a lot of free software to support those doing extensive text processing. Lastly, Appendix E is a Glossary for technical terms from the book. This is very much an educational book, and would be suitable for classroom work at the University level, beyond the introductory programming level; in fact, as part of a curriculum to teach programming using Python at the University level, this would be an excellent text for the second course.

One of the highlights of the book is that each chapter is concluded with a problem and discussion section. These are of the highest quality I have encountered in computer texts. Rather than overwhelming the reader with a large number of problems, the author has obviously given a lifetime of thought in coming up with a few key problems that are meant to stimulate thought, creativity, and ultimately understanding and growth in the reader. I will be coming back to the problems often, as they cannot be absorbed quickly anyway; they require thought. These would be most useful in a classroom environment; but as they are accompanied by excellent discussion material, and backed up by the author's web site, the individual reader will be well served also.

The book is more than the sum of its parts. It will be a most useful reference source for when I am doing various text related tasks for some time to come, and it was also a delightful and educational quick read in the here and now. It also amply illustrates the centrality of text processing in all areas of computer science, and I am confident that the book will be useful and educational for all programmers, whatever their area of expertise.

To sum it all up, this book is educational. It is also beautifully bound and printed, and excellently written. I rate it five stars, my highest rating, and heartily recommend its purchase.

Ron Stephens

I've been programming computers in various capacities since I was in my early teens (the mid-1970s) and I've been through a number of languages. Not long ago I discovered Python, and I suspect I won't need to learn any other languages for quite a long time. Guido van Rossum is a wizard.

If you're interested in learning Python, don't start here. If you've got some programming background already, Guido's tutorial (which comes bundled with the Python download) will be enough to get you rolling. I personally recommend all of O'Reilly's books on the subject (_Learning Python_ for the absolute beginner, Mark Lutz's idiosyncratic but highly useful _Programming Python_ for the next level up, the magisterial _Python Cookbook_ for pretty much anybody, and the _Nutshell_ book to be placed permanently next to your keyboard). There are others as well, and after you've gotten started, you'll be a better judge than I am of what will be most useful to you. (But I'd skip the vastly overpriced and not-very-deep _Python Programming Patterns_ unless you can buy it used.)

This one's for later; although it does offer some beginning instruction in Python, it isn't really an introductory book. However, if you do any text processing with Python -- which you almost undoubtedly do if you use Python at all -- then you _do_ want this book even if you don't know it yet.

Most of what you'll want to know is in chapter two, which sets out the basics of string processing in Python. The other, fancier stuff in the later chapters may be handy sometimes, but author David Mertz himself will tell you not to overcomplicate things; if you can do what you need to do using string operations, do so.

Read the rest of it too, though. There's good stuff here on e.g. regular expressions and parsing that you'll find interesting and possibly useful. Just don't rush out and start trying to apply it when it isn't necessary.

Mertz is an excellent teacher. He tends to approach things from a foundation of "functional programming" -- of which I'm not particularly a fan, but he has a healthy sense of its limitations and his comments on the subject are refreshing. (If you're interested in functional programming, get a book on Haskell, which is actually a very cool language. But me, I like imperative languages just fine and I don't have any problem with "side effects" as long as they're deliberate or at least controlled.) At any rate, Mertz won't lock you in to a functional approach, but he will teach you some function-oriented stuff that will be useful to you no matter what your preferred programming style.

And his exposition is well organized and wonderfully lucid. If you're the sort of person who likes books that have a chapter zero, you'll enjoy his style.

Unless you have a strong programming background, then, you probably won't want to start your Python bookshelf with this one. But I recommend making it one of your first five.

Also, in the area of Regular Expressions the examples didn't directly use the Python library, instead a wrap around function was used for the many examples and that detracted from using the book as a reference book for this purpose.

I found that Python has several different ways to do string processing. Also, some of those ways come up with conflicting results. At the time of this writing the authors of Python are re-organizing and improving this area.

What is truly great about the book is the discussion of state machines, parsers, and functional programming. Although these topics detract from the focus on string processing somewhat this book is perhaps the only popular Python book out there that does these topics justice. I thought they were very well written.

My overall complaint is that this book includes too many things outside of text processing using the core Python language. But other readers may appreciate this aspect more than I did. If you want coverage on handling email specifically, the author covers that. Same with HTML processing and other specialized topics. I just wanted to low down on using the full string processing capabilities of the core Python language -- not necessarily all the specialized libraries.

I found string processing to be messy with Python but found Ruby to be much easier. That is perhaps because Ruby is a newer language and it has some features of Perl built in. Ruby however does not have the extent of libraries available like Python, nor does it have as nice of Windows GUI.

Overall, if you are looking for a book on text processing this is the only book out there, and a big plus with this book is what you will learn on function programming, state machines and parsers.

The author worked hard to produce a book in this specialized area. He has lots of code examples. Highly recommended for Python programmers.

John Dunbar
Sugar Land, TX