So what is Python? Briefly, it is a computer programming language and a corresponding set of software tools and libraries. It was originally developed in the early 1990s by Guido van Rossum, and it is now actively maintained by dozens of programmers around the world (including van Rossum).

Python was designed to be easy to read and learn. Compared with programs written in most other programming languages, Python programs look neat and clean: Python has few unnecessary symbols, and it uses straightforward English names instead of the cryptic syntax common in other languages (Ruby and Perl, I’m looking at you!).

Python is a very productive language: Once you’re proficient with Python, you can get more done with it in less time than you can in most other programming languages. Python supports—but doesn’t force you to use—object-oriented programming (OOP).

Python comes with a wide range of ready-made libraries that can be (freely!) used in your own programs; as some Python programmers like to say, Python comes with “batteries included.”

One of the most important features of Python is its maintainability: Since Python programs are relatively easy to read and modify, they are easy for programmers to keep up to date. Program maintenance can easily account for 50 percent or more of the work a programmer does, and so Python’s support for maintenance is a big win in the eyes of many professionals.

Finally, a word about the name. According to Python’s originator, Guido van Rossum, Python was named after the Monty Python comedy troupe. Despite this mirthful origin, Python now uses a pair of iconic blue and yellow snakes—presumably pythons—as its standard symbol.

While Python is a general-purpose language that can be used to write any kind of program, it is especially popular for the following applications:

Of course, Python isn’t the best choice for all kinds of programming projects. Python is often less efficient than languages such as Java, C, and C++. So, for example, you wouldn’t use Python to create a new operating system.

But when you need to minimize the amount of time a programmer spends on a project, Python is often an excellent choice.

While there is no recipe for writing programs, it is helpful to understand the basic steps that all programmers follow.

The programming process

1. Determine what your program is supposed to do—that is, figure out its requirements.

2. Write the source code (in our case, the Python code) in IDLE (short for Python’s Integrated Development Environment) or any other text editor. Python source code files end with .py: web.py, urlexpand.py, clean.py, and so on. This is often the most interesting and challenging step, and it often involves creative problem solving.

3. Convert the source code to object code using the Python interpreter. Python puts object code in .pyc files. For example, if your source code is in urlexpand.py, its object code will be put in urlexpand.pyc.

4. Run, or execute, the program. With Python, this step is usually done immediately and automatically after step 2 is finished. Thus, in practice, Python programmers rarely work directly with object code or .pyc files.

5. Finally, check the program’s output. If errors are discovered, go back to step 1 to try to fix them. The process of fixing errors is called debugging. For large or complex programs, debugging can sometimes take up most of the program development time, so experienced programmers try to design their programs in ways that will minimize debugging time.

As Figure 1.1 shows, this is an iterative process: You write your program, test it, fix errors, test it again, and so on until the program behaves correctly.

Figure 1.1. The basic steps of writing any computer program. Typically, after you check your program output, you find errors and so must go back to the code-writing step to fix them.

Lingo Alert

We typically call the contents of a .py file a program, source code, or just code.

Object code is sometimes referred to as executable code, the executable, or even just software.

Python is a hands-on language, so now we will see how to install it on your computer.