What is Python?

Python is a high-level interpreted programming language with an object-oriented structure. It offers a vast number of libraries that make complex implementations easy, and good features that makes it the first choice to implement a lot of applications.

Hello Python

Let’s start with a simple "Hello, Python!" example. open your preferred code editor and put the below code in it then save it as file with the name hello.py:

print("Hello, world!")

Running Python

Python has two versions: Python 2 and Python 3. In this article, we will focus on Python 3.

To install the Python interpreter on a Linux OS, you can use the default system installation or install it for Debian-based Linux using the following command:

$ sudo apt install python3

For security and compatibility reasons, it is recommended to run Python in a virtual environment. This allows you to create a temporary environment specific to your project and its required libraries.

Virtual Environment

To install a virtual environment on Linux, use the following command:

sudo apt install python3-venv

To create a virtual environment named "myenv", use the following command:

python3 -m venv myenv

To activate the virtual environment, use the following command:

source ./myenv/bin/activate

Writing Python Code

There are two ways to write Python code:

Interactive Python (REPL)

REPL stands for Read => Evaluate => Print => Loop. It allows you to run individual Python statements sequentially.
You can enter the REPL mode by running python3 command in shell

python3

Python 3.9.6 (default, Feb  3 2024, 15:58:27) 
[Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

Then you can run any python command and see the output of it immediately

For example:

>>> print("Hello, world!")

Python Scripts

The second way that you can write Python code in script files with the ".py" extension and run them using the Python interpreter. To run a script named "example.py", use the following command:

python3 example.py

In Python, spacing and indentation are crucial because they define the structure of code blocks. The indentation level determines which statements belong to a specific block.

Python PEPs:

Python follows a style guide and best practices known as Python Enhancement Proposals (PEPs). For example, PEP8 provides guidelines for code style and indentation.

Now, let’s dive into the first lesson.