Chapter 1. An Overview of Python Essentials
Devops, the combination of software development with information technology operations, has been a hot field during the last decade.
Traditional boundaries between software development, deployment, maintenance, and quality assurance are broken, enabling more integrated
teams. Python has been a popular language both in traditional IT operations and in the DevOps due to its combination of flexibility, power, and
ease of use. The Python programming language was created in the early 1990s for use in system administration. It has been a great success in
this area and gained wide adoption. It is a general-purpose programming language used in just about every domain. Visual effects and the film
world is another prominent Python success story. More recently, it has become the defacto language in data science and machine learning. It has
been used across industries from avian to bioinformatics. Modern Python has an extensive arsenal of tools to cover the wide-ranging needs of its
users. Learning the whole Python Standard Library (the capabilities that come with any Python installation), would be a daunting task. If you
add to it learning all of the third party packages ( that enliven the Python ecosystem, it would be an immense undertaking. The good news is that
you don’t need to. You can become a powerful DevOps practitioner with only a small subset of Python.
In this chapter, we draw on our decades of Python DevOps experience to teach only the elements of the language that you need. These are the
parts of Python you use daily. They form the essential toolbox to get things done. Once you have these core concepts down, you can add more
complicated tools, and indeed this is touched in more advanced features in later chapters.
Installing and Running Python
If you want to try the code in this overview, you need version Python 3.7 or later installed (the latest release is 3.7.3 as of this writing), and
access to a shell. In Os X, Windows and most Linux distributions, you can open the terminal application to access a shell. To check the version
of Python you are using, open a shell and type python --version.
$ python --version
Python 3.7.3
Python installers can be downloaded directly from the Python.org website. Alternatively, you can use a package manager such as Apt, RPM,
MacPorts, Homebrew, Chocolatey, or many others.
The Python Shell
The simplest way to run Python is to use the built-in interactive interpreter. Just type python in a shell. You can then interactively run Python
statements. Type exit() to exit the shell.
$ python
Python 3.7.0 (default, Sep 23 2018, 09:47:03)
[Clang 9.0.0 (clang-900.0.38)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 1 + 2
3
>>> exit()
Python scripts
Python code runs from a file with the py extension.
# This is my first Python script
print("Hello world!")
To invoke the script, in a shell run python followed by the file name.
$ python hello.py
Hello world!
Python scripts are the way most production Python code runs.
IPython
Besides the built-in interactive shell, several third-party interactive shells run Python code. One of the most popular is IPython. IPython offers
introspection (the ability to dynamically get information about objects), syntax highlighting, special magic commands (which we touch on later
in this chapter), and many more features making it a pleasure to use for exploring Python. To install IPython, use the Python package manager,
1. An Overview of Python Essentials
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