Introduction to Python scripting

Python has many advantages when it comes to picking it for scripting. Before we dig deep into the Python scripting landscape, let’s take a look at these advantages and new features available in Python 3.

Why choose Python?

There are many reasons to choose Python as your main programming language. Importantly, many security tools are written in Python. This language offers many opportunities for extending and adding features to tools that are already written. Let’s look at what else Python has to offer us:

• It is a multi-platform and open source language.
• It is a simple, fast, robust, and powerful language.
• Many libraries, modules, and projects focused on computer security are written in Python.
• A lot of documentation is available, along with a very large user community.
• It is a language designed to make robust programs with a few lines of code, something that is only possible in other languages after including many characteristics of each language.
• It is ideal for prototypes and rapid-concept tests (Proof of Concept).

Multi-platform capabilities and versions

The Python interpreter is available on many platforms (Linux, DOS, Windows, and macOS X). The code that we create in Python is translated into bytecode when it is executed for the first time. For that reason, in systems in which we are going to execute our programs or scripts developed in Python, we need the interpreter to be installed.

In this book, we will work with Python version 3.7. If you’re starting to write some new Python code today, you should use Python 3. It’s important to be aware that Python 2 is end of life and will no longer receive security patches, so users should upgrade their code to Python 3.

If you have Python 2 code that you can upgrade to Python 3, you should do that as well. But if you’re like most companies with an existing Python 2 code base, your best option might well be to upgrade incrementally, which means having code that works under 2 and 3 simultaneously. Once you’ve converted all of your code, and it passes tests under both Python 2 and 3, you can flip the switch, joining the world of Python 3 and all of its goodness.

Tip

PEPs (Python Enhancement Proposals) are the main forums in the Python community for proposing new features or improvements to the Python core language. They enable the community to review, discuss, and improve proposals. Popular tools such as pep8 and flake8 enforce these rules when run on a Python file. The main PEP index can be found at http://python.org/dev/peps.

Python 3 features

Much has been written about the changes in Python 2 and 3. An extensive collection of such information is available at https://python-future.org. This site offers the futurize and pasteurize packages, as well as a great deal of documentation describing the changes between versions, techniques for upgrading, and other things to watch out for.

Some of the most important new features that Python 3 offers are as follows:

• Unicode is supported throughout the standard library and is the default type for any strings defined.
• The input function has been renewed.
• The modules have been restructured.
• The new asyncio library, which is part of the standard library, gives a defined way to execute asynchronous programming in Python. This makes it easy to write concurrent programs enabling you to make the most of your new-generation hardware.
• Better exception handling: in Python 2.X, there were lots of ways to throw and catch exceptions; with Python 3, error handling is cleaner and improved.
• Virtualenv is now part of the standard Python distribution.

  Tip

  If you are new to Python, you should start with Python 3 since many things have been improved and more thoughtfully designed. If you want to use old code or specific packages and libraries that are still based on Python 2, you should, of course, use this version, especially in those cases where porting would be complex. Exploring old Python 2 code with tools such as 2to3 and porting, if necessary, is a good place to start.

Now that you know the reason for choosing Python as a scripting language and the main features of Python 3, let’s move on to learning about the main data structures available in Python.