python-tutorials/intro.asciidoc

[[intro]]
== Introduction

Python is one of those rare languages which can claim to be both _simple_ and _powerful_.  You will
find yourself pleasantly surprised to see how easy it is to concentrate on the solution to the
problem rather than the syntax and structure of the language you are programming in.

The official introduction to Python is:

__________________________________________________
Python is an easy to learn, powerful programming language. It has efficient high-level data
structures and a simple but effective approach to object-oriented programming. Python's elegant
syntax and dynamic typing, together with its interpreted nature, make it an ideal language for
scripting and rapid application development in many areas on most platforms.
__________________________________________________

I will discuss most of these features in more detail in the next section.

.Story behind the name
**************************************************
Guido van Rossum, the creator of the Python language, named the language after the BBC show "Monty
Python's Flying Circus". He doesn't particularly like snakes that kill animals for food by winding
their long bodies around them and crushing them.
**************************************************

=== Features of Python

 Simple ::
Python is a simple and minimalistic language. Reading a good Python program feels almost like
reading English, although very strict English! This pseudo-code nature of Python is one of its
greatest strengths. It allows you to concentrate on the solution to the problem rather than the
language itself.

Easy to Learn ::
As you will see, Python is extremely easy to get started with. Python has an extraordinarily simple
syntax, as already mentioned.

Free and Open Source ::
Python is an example of a _FLOSS_ (Free/Libré and Open Source Software). In simple terms, you can
freely distribute copies of this software, read its source code, make changes to it, and use pieces
of it in new free programs. FLOSS is based on the concept of a community which shares
knowledge. This is one of the reasons why Python is so good - it has been created and is constantly
improved by a community who just want to see a better Python.

High-level Language ::
When you write programs in Python, you never need to bother about the low-level details such as
managing the memory used by your program, etc.

Portable ::
Due to its open-source nature, Python has been ported to (i.e. changed to make it work on) many
platforms. All your Python programs can work on any of these platforms without requiring any
changes at all if you are careful enough to avoid any system-dependent features.
+
You can use Python on GNU/Linux, Windows, FreeBSD, Macintosh, Solaris, OS/2, Amiga, AROS, AS/400,
BeOS, OS/390, z/OS, Palm OS, QNX, VMS, Psion, Acorn RISC OS, VxWorks, PlayStation, Sharp Zaurus,
Windows CE and PocketPC!
+
You can even use a platform like http://kivy.org[Kivy] to create games for your computer _and_ for
iPhone, iPad, and Android.

[[interpreted]]
Interpreted ::
This requires a bit of explanation.
+
A program written in a compiled language like C or C\++ is converted from the source language
i.e. C or C++ into a language that is spoken by your computer (binary code i.e. 0s and 1s) using a
compiler with various flags and options. When you run the program, the linker/loader software
copies the program from hard disk to memory and starts running it.
+
Python, on the other hand, does not need compilation to binary. You just _run_ the program directly
from the source code. Internally, Python converts the source code into an intermediate form called
bytecodes and then translates this into the native language of your computer and then runs it. All
this, actually, makes using Python much easier since you don't have to worry about compiling the
program, making sure that the proper libraries are linked and loaded, etc. This also makes your
Python programs much more portable, since you can just copy your Python program onto another
computer and it just works!

Object Oriented ::
Python supports procedure-oriented programming as well as object-oriented programming. In
_procedure-oriented_ languages, the program is built around procedures or functions which are
nothing but reusable pieces of programs. In _object-oriented_ languages, the program is built
around objects which combine data and functionality. Python has a very powerful but simplistic way
of doing OOP, especially when compared to big languages like C++ or Java.

Extensible ::
If you need a critical piece of code to run very fast or want to have some piece of algorithm not
to be open, you can code that part of your program in C or C\++ and then use it from your Python
program.

Embeddable ::
You can embed Python within your C/C\++ programs to give _scripting_ capabilities for your
program's users.

Extensive Libraries ::
The Python Standard Library is huge indeed. It can help you do various things involving regular
expressions,documentation generation, unit testing, threading, databases, web browsers, CGI, FTP,
email, XML, XML-RPC, HTML, WAV files, cryptography, GUI (graphical user interfaces), and other
system-dependent stuff. Remember, all this is always available wherever Python is installed. This
is called the _Batteries Included_ philosophy of Python.
+
Besides the standard library, there are various other high-quality libraries which you can find at
the http://pypi.python.org/pypi[Python Package Index].

Summary ::
Python is indeed an exciting and powerful language. It has the right combination of performance and
features that make writing programs in Python both fun and easy.

=== Python 2 versus 3

You can ignore this section if you're not interested in the difference between Python 2 and
Python 3. But please do be aware of which version you are using.

Remember that once you have properly understood and learn to use either of them, you can easily
learn the changes between the two versions and adapt easily. The hard part is learning programming
and understanding the core Python language itself. That is our goal in this book, and once you have
achieved that goal, you can easily use Python 2 or Python 3 depending on your situation.

For details on differences between Python 2 to Python 3, see:

- http://lwn.net/Articles/547191/[The future of Python 2]
- https://wiki.ubuntu.com/Python/3[Python/3 page on the Ubuntu wiki]

=== What Programmers Say

You may find it interesting to read what great hackers like ESR have to say about Python:

. _Eric S. Raymond_ is the author of "The Cathedral and the Bazaar" and is also the person who
coined the term _Open Source_. He says that http://www.python.org/about/success/esr/[Python has
become his favorite programming language]. This article was the real inspiration for my first brush
with Python.

. _Bruce Eckel_ is the author of the famous 'Thinking in Java' and 'Thinking in C++' books. He says
that no language has made him more productive than Python. He says that Python is perhaps the only
language that focuses on making things easier for the programmer. Read the
http://www.artima.com/intv/aboutme.html[complete interview] for more details.

. _Peter Norvig_ is a well-known Lisp author and Director of Search Quality at Google (thanks to
Guido van Rossum for pointing that out). He says that
https://news.ycombinator.com/item?id=1803815[writing Python is like writing in pseudocode]. He says
that Python has always been an integral part of Google. You can actually verify this statement by
looking at the http://www.google.com/jobs/index.html[Google Jobs] page which lists Python knowledge
as a requirement for software engineers.