Chapter 1: Setting Up Your Python Development Environment

Before diving into writing Python code, it’s essential to have a clean, efficient, and testable development environment. This chapter covers:

• Installing Python
• Setting up virtual environments
• Choosing the right IDE or editor
• Managing dependencies
• Creating your first Python script
• Writing and running your first unit test

1.1 Installing Python

Python frequently updates with new features, security patches, and performance improvements. Installing a current and supported version (Python 3.11 or higher) ensures compatibility with modern frameworks like FastAPI, Django, and scikit-learn.

Download Python:

Official website: https://www.python.org/downloads/

Installation Settings:

• On Windows: Make sure to check "Add Python to PATH".
• On Mac/Linux: Use brew install python3 (Mac) or your Linux package manager.

Verify Installation:

bash
python --version

Expected Output:

bash
Python 3.11.x

1.2 Setting Up Virtual Environments

A Python Virtual Environment is an isolated environment that allows you to manage dependencies, packages, and even Python versions on a per-project basis—without affecting the global Python installation on your system.

Why Use Virtual Environments?

1. Dependency Isolation: Different projects may require different versions of the same package (e.g., Django 2.x vs 3.x). Virtual environments keep these dependencies separate.
2. Prevent Package Conflicts: Installing packages globally can lead to conflicts between projects.
3. Environment Reproducibility: Helps ensure that your production environment and local development environment use the exact same package versions.
4. Safe Experimentation: Easily install, update, or remove packages within a project without risking breaking other Python projects.

Popular Tools for Managing Virtual Environments

• venv (built-in with Python 3.3+)
• virtualenv (third-party, older but still widely used)
• pipenv (combines pip + venv, adds dependency management via Pipfile)
• Poetry (modern dependency management and packaging tool)

Using venv (Built-in for Python 3.3+):

bash
1# Create a virtual environment
2python -m venv venv
3
4# Activate it:
5# Windows
6venv\Scripts\activate
7
8# Mac/Linux
9source venv/bin/activate

Confirm the Environment:

bash
which python

or on Windows:

bash
where python

1.3 Choosing Your IDE / Editor

Choosing the right Integrated Development Environment (IDE) can greatly enhance your productivity as a Python developer. IDEs offer helpful features like syntax highlighting, code completion, linting, debugging tools, virtual environment management, and built-in terminals.

Popular choices:

Throughout ths tutorial we will primarily use PyCharm and Jupyter Notebook. Instruction for downloading and setting up PyCharm may be found here. Instruction for downloading and setting up Jupyter Notebook may be found here.

1.4 Managing Dependencies

Keeping track of dependencies is crucial for testability and reproducibility.

Install packages:

bash
pip install requests

pip is the package installer for Python. The command above install the requests library.

Freeze dependencies:

bash
pip freeze > requirements.txt

The command pip freeze > requirements.txt is used to create a file named requirements.txt that lists all the packages installed in your current Python environment and their exact versions.

Install from requirements later:

bash
pip install -r requirements.txt

This command is used to install all the Python packages listed in a file named requirements.txt.

For larger projects: Consider using pipenv or poetry for better dependency management.

1.5 Your First Python Script

Let’s create a simple Python script: greet.py

File: greet.py

To start open PyCharm. Click on the File menu. Select New Project.... Create a Pure Python project.

When a new project created click on the File menu, and select New File or Directory. Select File from the dropdown on the Project pane, and enter file name greet.py. Once the file is created, enter the following code in the file.

greet.py
1def greet(name):
2    return f"Hello, {name}!"
3
4if __name__ == "__main__":
5    user_name = input("Enter your name: ")
6    print(greet(user_name))

Run it:

To run the program, click on the terminal icon on the left hand side of the IDE. Type the following command in the terminal.

bash
python greet.py

Expected Output:

bash
Enter your name: Walid Newaz
Hello, Walid Newaz!

1.6 Writing Your First Unit Test

Let’s test the greet function using pytest.

Step 1: Install pytest:

Enter the following command in your terminal.

bash
pip install pytest

This will install the pytest library.

Step 2: Create a test file: test_greet.py

Enter the following code in the file:

test_greet.py
1from greet import greet
2
3def test_greet():
4    assert greet("Alice") == "Hello, Alice!"
5    assert greet("Bob") == "Hello, Bob!"

Step 3: Run your test:

Run all tests in the current directory by typing the following command in your terminal:

bash
pytest

Expected Test Output:

bash
collected 1 item

test_greet.py .                                  [100%]

1 passed in 0.00s

1.7 Optional: Setting Up Git for Version Control

Basic Git Workflow:

bash
git init
git add .
git commit -m "Initial commit with greet function and test"

Consider pushing to GitHub later for backup and collaboration.

Conclusion

You now have:

• Python installed and configured
• A virtual environment running
• A dependency management workflow
• Your first Python script and test case

What is Next?

In Chapter 2: Python Syntax and Core Concepts, we’ll cover:

• Variables
• Loops
• Conditionals
• Functions
• Building your first CLI calculator (with tests)