So what is Python? Simply put, Python is a programming language. It was initially developed by Guido van Rossum in the late 1980's in the Netherlands. Guido continues to be actively involved in guiding the development and evolution of the language, so much so that he's been given the title "Benevolent Dictator for Life", or, more commonly, BDFL. Python is developed as an open-source project and is free to download and use as you wish. The non-profit Python Software Foundation manages
Python's intellectual property, plays a strong role in promoting the language, and in some cases funds its development.

On a technical level, Python is a strongly typed language. This means that every object in the language has a definite type, and there's generally no way to circumvent that type. At the same time, Python is dynamically typed, meaning that there's no type-checking of your code prior to running it. This is in contrast to statically typed languages like C++ or Java where a compiler does a lot of type-checking for you, rejecting programs which misuse objects. Ultimately, the best description of the Python type system is that it uses duck-typing where an object's suitability for a context is only determined at runtime. We'll cover this in more detail in Chapter 8, Defining new types with classes.

Python is a general-purpose programming language. It's not intended for use in any particular domain or environment, but instead can be fruitfully used for a wide variety of tasks. There are, of course, some areas where it's less suitable than others – for example in extremely time-sensitive or memory-constrained environments – but for the most part Python is as flexible and adaptable as many modern programming language, and more so than most.

Python is an interpreted language. This is a bit of a misstatement, technically, because Python is normally compiled into a form of byte-code before it's executed. However, this compilation happens invisibly, and the experience of using Python is normally one of immediately executing code without a noticeable compilation phase. This lack of an interruption between editing and running is one of the great joys of working with Python.

The syntax of Python is designed to be clear, readable, and expressive. Unlike many popular languages, Python uses white-space to delimit code blocks, and in the process does away with reams of unnecessary parentheses while enforcing a universal layout. This means that all Python code looks alike in important ways, and you can learn to read Python very quickly. At the same time, Python's expressive syntax means that you can get a lot of meaning into a single line of code. This expressive, highly-readable code means that Python maintenance is relatively easy.

There are multiple implementations of the Python language. The original – and still by far the most common – implementation is written in C. This version is commonly referred to as CPython. When someone talks about "running Python", it's normally safe to assume that they are talking about CPython, and this is the implementation that we'll be using for this book.

Other implementations of Python include:

• Jython, written to target the Java Virtual Machine

• IronPython, written to target the .NET platform

• PyPy, written (somewhat circularly) in a language called RPython which is designed for developing dynamic languages like Python

These implementations generally trail behind CPython, which is considered to be the "standard" for the language. Much of what you will learn in this book will apply to all of these implementations.