Programming Python, Part II

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Having covered some advanced features in Part I, it's time to include some basics.
Python 2.5

During the process of writing this article, with much excitement and fanfare, Python 2.5 was released. It is the most important release in almost two years, and it comes with many promises.

It promises to be more reliable due to improvements in the testing procedures used by the Python development team. It now has Buildbot, a program that continuously builds and tests Python, and whenever there's something wrong, it raises an alarm for all the world to see. The shame of being the developer who made the error will make all the developers more careful—at least, that's what happened to me when I had a Buildbot watching my code.

For some, like this author who had a new release at the worst possible time, the most important thing is that Python 2.5 is backward-compatible. All that you've learned here will work. And, not only will it work, it is still the way to do it.

The new release also promises to be faster and has many new advanced features, including new modules and packages. The future is bright for Python and Python coders.

What Now?

This was nothing but a short introduction to Python; there's still much to learn. A good place to start is the official Python Tutorial. You also can read Dive Into Python, a book that you can buy or read for free on the Web. And, of course, a lot of other books and tutorials are available. I learned Python mainly from the Python Tutorial, which is very good.

Whenever you are creating a program in Python, never, and I repeat, never, do anything without checking whether it has been done before. Python has a lot of features and a lot of built-in libraries. And, if that isn't enough, there are hundreds, maybe thousands of third-party Python libraries. In fact, the huge amount of code that's already written in Python is one of the reasons to use it.

The first stop is Python's Documentation. There we have the previously mentioned tutorial, the library reference and the language reference.

The language reference can be a bit hard to use and understand. Programming languages tend to be difficult to understand and so are their references, which often have exclusive jargon, such as lexical analysis, tokens, identifiers, keywords or delimiters. This piece of documentation can be particularly useful in showing how to use language constructs, such as for, if, while and more complex ones that I haven't mentioned, such as yield, break or continue.

The library references let us know about all the classes, methods and functions that Python already provides. It is so important and useful that I always have it open when I am programming on Python. In the second chapter, you can read about the built-in functions and classes. Getting familiar with them is always useful. The rest of the documentation is very specific, and each chapter deals with subjects ranging from runtime internals to string, from the Python debugger to some generic operating systems services. In that chapter, a very important module is documented: os. I can't remember making a single program that didn't use that module.

Finding what you want in so much documentation can be a difficult task. A trick that I find very useful is to use Google to search in a specific site. That is achieved by adding “site:python.org” or “site:docs.python.org” to the search query. The first one is more generic and sometimes leads to countless mailing-list posts that have nothing to do with what you are looking for. In that situation, use the second one. To give it a try, search for “print site:python.org” or “options site:python.org”.

What if all of your searches return nothing? Then, you need to do a broader search to find some third-party libraries or frameworks. If you want to make a graphical user interface, I recommend both PyGTK and PyQt, both are very good and include support for their respective desktops, GNOME and KDE. I've heard good opinions of wxPython, but I've not used it myself.

If you want to build a Web application, I see two paths. If you want something not so spectacular but that gets you there fast, I recommend Django. Django is very similar to Ruby on Rails. It's a framework in which you use the model-view-controller paradigm and a relational database such as MySQL or PostgreSQL; both are well supported on Python.

The other way to build Web sites (that I know of) is Zope. Zope is a big framework with a Web server and object-oriented database. The database is different from other relational databases, and it is very powerful. It allows you to store information in a much more flexible way. Zope 3—I don't recommend the previous versions unless you have to use the award-winning content management system Plone—is prepared to help you build reliable and robust code by means of interfaces, unit testing, adapters and much more.

If you need to build any kind of dæmon—those little applications running in the background making the earth turn—take a look at Twisted Matrix. Twisted Matrix is an event-based framework that solves a lot of the common problems of building dæmons, including separation of protocol and logic. It comes with many protocols already built in, and it allows you to create new protocols. A proof of its usefulness is that Zope, after years of shipping its own Web sever, has migrated to using the Twisted Matrix HTTP server.

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error?

csshef's picture

cool = blog.Post("Cool", "Python is cool")

I can't get the above line to work. Is that correct?

error?

ejournal's picture

Were you using Emacs and following the instructions in part I? If so, the class "Post" will be part of the module "blog". If not, you must arrange for that yourself - the article explains.

If I understand correctly. I'm not a Python programmer. :)

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