Introduction to Python and Basic Syntax

2.2. Introduction to Python and Basic Syntax#

Python is a high-level, interpreted programming language with a simple and intuitive syntax. It’s widely used in data science, automation, artificial intelligence, and scientific programming.

Let’s start with the classic “Hello, world!”.

print("Hello, world!")

2.2.1. Command Line#

It’s possible to execute Python commands directly from the terminal.

In the terminal, type:

python3

You can also run a saved script:

python3 hello.py

Or start a Jupyter Notebook with:

jupyter-notebook

2.2.2. Jupyter Notebook#

Jupyter Notebook is a powerful tool for data analysis, as it allows you to write code and explanatory text in a single interactive environment.

Each cell can contain code (Python) or text (Markdown).

To run a cell: Shift + Enter

  • Run cell and go to the next: Shift + Enter

  • Run cell and stay there: Ctrl + Enter (or Cmd + Enter on Mac)

  • Insert new cell below: Esc, then press B

  • Insert new cell above: Esc, then press A

  • Change cell to Markdown: Esc, then press M

  • Change cell to Code: Esc, then press Y

These shortcuts greatly help speed up writing and editing your notebook!

2.2.3. Indentation#

Indentation defines code blocks in Python. Indentation errors are common when starting out.

Use 4 spaces or Tab.

Example:

# Correct
if True:
    print("Correctly indented!")

# Incorrect
if True:
print("Indentation error!") # This causes an error

2.2.4. Comments#

Comments are text snippets ignored by the Python interpreter. They serve to explain what the code does.

There are two main types:

  • Single-line comment (#)

  • Multi-line comment (with """ or ''', although this is more commonly used for docstrings)

Tip: Write clear and direct comments, especially when the code is complex.

  • Comment selected line(s):

    • Ctrl + / (Windows/Linux)(US keyboard layout)

    • Ctrl + ; (Windows/Linux)(ABNT keyboard layout)

    • Cmd + / (Mac)

"""
This is a multi-line
comment block. It can be used
to document larger sections.
"""
print("Block commented above.")

Block commented above.
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