Until now error messages haven't been more than mentioned, but if you have tried out the examples you have probably seen some. There are (at least) two distinguishable kinds of errors: syntax errors and exceptions.

If you quit from the Python interpreter and enter it again, the definitions you have made (functions and variables) are lost. Therefore, if you want to write a somewhat longer program, you are better off using a text editor to prepare the input for the interpreter and running it with that file as input instead. This is known as creating a script. As your program gets longer, you may want to split...

Google is now letting web sites submit an xml file that lists urls and some information about how often the pages change, and how important the page is relative to other pages. Basically, it gets you to do part of the work for them - which we would hope helps everyone

This section will help you to put a GUI (graphical user interface) in your Python program. We will use a particular GUI library: PyGTK. We've chosen this because it is reasonably light-weight and our goal is to embed light-weight GUI interfaces in an (possibly) existing application. For simpler GUI needs, consider EasyGUI, which is also described below.

So, you want to learn the Python programming language but can't find a concise and yet full-featured tutorial. This tutorial will attempt to teach you Python in 10 minutes. It's probably not so much a tutorial as it is a cross between a tutorial and a cheatsheet, so it will just show you some basic concepts to start you off. Obviously, if you want to really learn a language you need to program in...

Python pickling support comes from the pickle module, and its cousin, the cPickle module. The latter was coded in C to provide better performance and is the recommended choice for most applications. We'll continue to talk about pickle, but our examples will actually make use of cPickle. Since most of our examples will be shown from the Python shell, let's start by showing how to import cPickle...

This second tour covers more advanced modules that support professional programming needs. These modules rarely occur in small scripts.

Floating-point numbers are represented in computer hardware as base 2 (binary) fractions. For example, the decimal fraction.

he modulus operator turns out to be surprisingly useful. For example, you can check whether one number is divisible by another if x % y is zero, then x is divisible by y. Also, you can extract the right-most digit or digits from a number. For example, x % 10 yields the right-most digit of x (in base 10). Similarly x % 100yields the last two digits.

The index you are using to access a list, string, or tuple is greater than its length minus one. Immediately before the site of the error, add a print statement to display the value of the index and the length of the array. Is the array the right size? Is the index the right value?

o far we've encountered two ways of writing values: expression statements and the print statement. (A third way is using the write() method of file objects; the standard output file can be referenced as sys.stdout.Often you'll want more control over the formatting of your output than simply printing space-separated values. There are two ways to format your output; the first way is to do all the...

When known to the interpreter, the script name and additional arguments thereafter are passed to the script in the variable sys.argv, which is a list of strings. Its length is at least one; when no script and no arguments are given, sys.argv[0] is an empty string. When the script name is given as '-' (meaning standard input), sys.argv[0] is set to '-'. When -c command is used, sys.argv[0] is set...

The Python interpreter is usually installed as /usr/local/bin/python on those machines where it is available; putting /usr/local/bin in your Unix shell's search path makes it possible to start it by typing the command.

Python is often compared to other interpreted languages such as Java, JavaScript, Perl, Tcl, or Smalltalk. Comparisons to C++, Common Lisp and Scheme can also be enlightening. In this section I will briefly compare Python to each of these languages. These comparisons concentrate on language issues only. In practice, the choice of a programming language is often dictated by other real-world...

Python is an interpreted, interactive, object-oriented programming language. Python is an interpreted, object-oriented, high-level programming language with dynamic semantics. Its high-level built in data structures, combined with dynamic typing and dynamic binding, make it very attractive for Rapid Application Development, as well as for use as a scripting or glue language to connect existing...