Customer Reviews

Data Munging with Perl

5 star:		(6)
4 star:		(4)
3 star:		(0)
2 star:		(1)
1 star:		(1)

 

 

I was perusing the shelves at my local bookstore, when this title jumped out and grabbed me. Not only is it a unique and interesting title (Something uncommon for computer books), but it is also the most succinct description of my job, and of Perl for that matter, that I have ever seen.

I am an avid reader, and in the interest of furthering my career most of my reading is work related. Normally, it takes me more than a month to read a book, though I am in the process of reading a half dozen or so at a time. I finished this book in less than a week. I couldn't put it down.

The thing that is so great about this book, is that it delves into the heart of what Perl does best (And was designed to do). Nine out of ten (more like ninety-nine out of one-hundred) jobs in Perl involve taking some sort of raw data, munging it, and spitting it out to some other process. This book is about doing that, many of the different forms that that can take, and some of the many techniques that perl (and a pragmatic approach) make available to do that.

While I hesitate to say that this is the best Perl book I've ever read (It's got some good competition), I can say that there is no application of Perl that I am aware of where this book and the principles it explores would not be of value. In my opinion this book belongs on every serious Perl programmer's bookshelf right next to the "Camel" and the "Cookbook".

Dave Cross's new book, published by Manning, which means it has a figure from an old guide to native dress of the peoples of the world on the cover instead of some kind of animal, tells everything you need to know about using Perl for what it is most suited for: manipulating data.

Starting with the source/filter/sink theory of data manipulation and demonstrating every tip and technique with clear and efficient examples, without severe digressions into mythological whimsy, this book would make an excellent second text on the Perl language, or a suitable first for someone who is good with programming languages.

Many of the techniques contained in it are of "trade secret" quality; they are the sort of write-the-number-of-gallons-of-paint-it-took-to-paint- the-room-on-the-back-of-the-light-switch-cover practices that until now had to be learned or happened upon by every programmer, alone, or by example, rather than in the context of a coherent theory.

The theoretical side, in which "munging" is defined and most software activity is described in terms of it, is clear enough that the book might be an interesting read for management, to answer the question "Just what is it about Perl that makes those who use it regularly so confoundedly fanatical?"

If you've ever been mystified by a Perl wizard who found it easier to export the records from the fancy GUI database into a comma delimited text file and then sort and display the data with mysterious little programs rather than use the GUI's native report generator, and want to find out why, or if you would like to become such a person yourself, or if you already are such a person but would like to get better at it, this book is for you.

This book isn't about arcane corners of Perl theory. It's about how to write Perl programs that perform the "simple" task of converting data from one format to another.

Need to get every headline from an RSS feed? Or report the three users with the most processes running, as listed by `ps`? Or extract the first paragraph from each of a thousand HTML files? Or make a .tsv file based on all the "From:" and "Subject:" lines in your mailbox file? If those sorts of tasks sound familiar to you, then this is the book you've been looking for. It has working code for doing these sorts of things, involving lots of different common kinds of formats.

By tech book standards, this book is short (300 pages), but it's clear and direct and to the point -- no bloat here. Every page tells you something you need to know, with useful examples for every idea that it explains.

It's a guide. David takes you through the different "data munging" tasks ( record oriented data ? binary data ? fixed-width data ? XML ? ) and shows you his proper ways of dealing with them ( or, at least, thinking about them ). It's not an encyclopedia of "data munging", the book is 300 pages and many of them ( too many, may be ) are detailed descriptions of useful CPAN modules ( which I wasn't reading as careful as the rest of the book, since POD was always enough ), so it covers only a usual data processing tasks letting you to go deeper by yourself for more advanced topics. After you'll finish it much less "data sources" will scare you - the solutions and references are inside.

As I said, it may be good for data-processing beginners, but Perl experts will hardly find lot's of new information in it.

P.S. I trust him and therefore follow his advices in every script I start to think of ( especially the one about "UNIX filter model" ).

This book, written by Perlmonk (www.perlmonks.org) David Cross, is an excellent, easy to read, and easy to follow guide into what Perl does best: Data Munging. For those who don't know, Munging Data means taking data from one format and putting it into another. Perl excels at this, and the author shows you the how and the why.

The author gives you enough information, and background to start working with the more advanced Perl functions like map, grep, pack, unpack, etc. It is possible to write Perl without ever having to use these modules, but David Cross shows you how they are more effective, more powerful. This book will expand your Perl vocabulary by leaps and bounds.

I know that some people would say that the book is too thin, and it is thinner than many computer books today, but the thickness of a book does not determine it's merit. Effective Perl Programming by Joseph Hall and Randal Schwartz is often cited as one of the best Perl books ever and it's thinner than this one.

If you are a junior to intermediate level programmer, and you want to improve your Perl skills, pick up this book. You won't be disappointed.

After reading this book I rewrote a pretty massive postscript pasrsing and munging system that I was having a lot of trouble with and felt like I did it the _right_ way. If you follow the author through his examples and actually read the book (which I was able to read almost straight through) I think that you will find yourself with a more long-view approach. And I think that makes this book valuable. And admit it, every time you read throgh a regex chapter you get a little more in the old noggin...

The quintessential Perl activity is data processing, particularly in a Unix environment, where output is piped into a script from some other program, transformed, and spat out again. Many people's first encounter with Perl will probably be in this task. David Cross's book shows how to do this with the minimum of fuss and the maximum of flexibility. It's not a Perl tutorial however, so you will need some basic knowledge of Perl, having read The Llama is enough. There is an appendix of 'essential Perl' to refresh your memory if you're a bit rusty.

The book begins by revising some of those basic Perl practices that come in handy for scripting, e.g. command line options, regular expressions and sorting. The second part of the book deals with parsing fairly simple data: traditional fixed-width record data (e.g. the column-based stuff that you often find as the output of old Fortran and C programs), unstructured data (e.g. doing word counts on text files), and formats such as CSV, PNG and MP3. This is the strongest section of the book, and contains lots of useful hands-on information.

The third part of the book deals with more modern forms of data files, in the shape of XML. Parsing HTML also gets a chapter to itself, after the author usefully demonstrates the limitations of any simple solution (e.g. using regexes), which provides pretty strong evidence in favour of the standard 'don't try it yourself, use a CPAN module' argument. The XML chapter itself covers the XML::Parser module in reasonable detail. However, there are now many more XML parsers in Perl out there, and XML::Parser is probably no longer the best solution (Grant McClean's Perl XML FAQ on the net has a good overview of the options). Excluding the seemingly obligatory 'here's a bunch of books and websites to learn more' chapter, the last proper chapter is on parsing, and the Rec::Descent module, and it's a very good gentle introduction.

If you're not working in a command line environment, there's not a whole lot here you're going to need. Equally, if you've been doing this sort of thing for a while, there's not much here that will be new to you, not all the subjects are explored in any great depth. And some of it (particularly the XML chapter) is a bit outdated and superficial, so I would knock off a star from my rating if you're more interested in the XML/HTML chapters.

But for the simpler tasks, e.g. parsing column based data, this is recommended. You're shown all the handy tricks you need such as piping, taking input from standard in as well as files, slurping paragraphs etc. My 4-star rating applies if this sounds like what you need: it's a clear, short and to-the-point book, which is definitely taking with you on your first journey into data munging.

With Data Munging with Perl David Cross joins the ranks of the top Manning authors such as Conway and Johnson, a book that is both an excellent guide to doing essential day to day tasks in perl and a delighful read.

Buy this book for the parsing section alone.

As a DBA, I bought this book to enhance my data manipulation skills with Perl but I found so much more in this compact book. David Cross provides many excellent code examples and explanations for common, non-database data manipulation tasks. For example: working on delimited and fixed-width text files and managing complex data structures in perl with array and hash refs. David has excellent communications skills as his examples and explanations taught me much about Perl that I did not previously understand completely. I also found the Chapter 4 on regular expressions to be one of the best and most concise. The only downside of this book is that I wish it had more pages to read! Regardless, it's a must-have perl book.

As a Peoplesoft developer, I was looking out for a tool for analyzing,formatting,cleaning large amount of data without need to put into a db table. Learned Perl and then jumped to this book. This book has just in time advice for doing that. Also it helps in developing perl skills for people like me who do not use perl on regular basis.Thanks!