Free Python tutorials in PDF

What is Python?

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You have decided to learn Python and I can only congratulate you. I will try to anticipate your questions and leave no one behind.

In this chapter, I will first explain what a programming language is. We will then briefly see the story of Python, so that you at least know where this language comes from! This chapter is theoretical but I urge you to read it anyway.

The final section will cover the installation of Python, an essential step to continue this tutorial. Whether you are working with Windows, Linux or Mac OS X, you will find precise explanations of the installation.

Come on, we attack!

A programming language? What is it ?

Human communication
No, this is not a biological or philosophical explanation, do not leave!
Very simply, if you come to understand these sequences of strange and disconcerting symbols that are the letters of the alphabet, it is because we respect certain conventions, in language and in writing. In French, there are rules of grammar and spelling, I do not teach you anything. You communicate by knowing more or less consciously these rules and by applying them more or less well, as the case may be.
However, these rules can easily be circumvented: no one can claim to know all the rules of French grammar and spelling, and few people care. After all, even if you make mistakes, people with whom you communicate can easily understand you.
When you communicate with a computer, however, it's very different.

My computer communicates too!

Yes, your computer communicates constantly with you and you communicate with him constantly. Okay, he tells you very rarely that he is hungry, that the summer promises to be scorching and that the last disc of this well-known band was crying.
There is nothing magic if, when you click on the small cross at the top right of the current application, it understands that it must close.

Machine language

In fact, your computer is also based on a language to communicate with you or with itself. The operations that a computer can perform at the base are most classic and consist of the addition of two numbers, their subtraction, their multiplication, their division, whole or not. And yet, these five operations are amply enough to run the most complex simulation software or super-realistic games.
All these programs work roughly the same way:

• a sequence of instructions written in machine language composes the program;
• when running the program, these instructions describe to the computer what to do (the computer can not guess).

By schematizing voluntarily, an instruction could ask the program to close if you click on the cross at the top right of your screen, or stay in the background if that is his pleasure. However, in machine language, such an action alone requires a large number of instructions.

But hey, you can imagine, talking with the computer in machine language, which includes only the binary, it is neither very rewarding nor very practical, and in any case not very funny.
We have invented programming languages to facilitate communication with the computer.

What can Python do?

Python is a powerful language that is both easy to learn and rich in possibilities. From the moment you install it on your computer, you have many features built into the language that we will discover throughout this book.

It is also very easy to extend the existing features, as we will see. Thus, there are so-called libraries that help the developer to work on particular projects. Several libraries can thus be installed to, for example, develop graphical interfaces in Python.

Concretely, that's what we can do with Python:

• small, very simple programs, called scripts, loaded with a very precise mission on your computer;
• complete programs, such as games, office suites, multimedia software, email clients ...
• very complex projects, such as software packages (set of several software that can work together, mainly used in the professional world).