Chapter 15: Virtual Environments and pip — Exercises¶

Overview¶

These exercises help you manage Python environments and dependencies using virtual environments and pip. By the end, you will confidently set up isolated development environments and manage project dependencies.

How to Use These Exercises¶

Create a folder called chapter-15 in your python-learning directory.
Follow the exercises to create and manage virtual environments.
Run commands in your terminal or command prompt.
Experiment with variations to deepen your understanding.

Warm-up Exercises¶

Exercise 1: Create and Activate a Virtual Environment¶

On Windows (Command Prompt):

# Create a virtual environment
python -m venv myenv

# Activate it
myenv\Scripts\activate

# You should see (myenv) in your prompt

On macOS/Linux:

# Create a virtual environment
python3 -m venv myenv

# Activate it
source myenv/bin/activate

# You should see (myenv) in your prompt

Once activated, verify the Python version:

python --version
which python  # or 'where python' on Windows

Deactivate the environment:

deactivate

Exercise 2: Install and List Packages¶

Activate your virtual environment, then:

# Install a package
pip install requests

# List installed packages
pip list

# Show details about a package
pip show requests

# Install a specific version
pip install requests==2.28.0

# Install multiple packages
pip install flask django

# Uninstall a package
pip uninstall requests

Exercise 3: Create a requirements.txt File¶

Create a file called requirements.txt:

requests==2.28.0
flask==2.2.0
pytest==7.1.0

Install all requirements:

pip install -r requirements.txt

Generate requirements from current environment:

pip freeze > requirements.txt

Exercise 4: Use Different Python Versions¶

Check available Python versions:

python --version
python3 --version
python3.10 --version  # if available

Create a virtual environment with a specific version:

# On Windows
python -m venv myenv_py310

# On macOS/Linux
python3.10 -m venv myenv_py310

Practice Exercises¶

Exercise 5: Set Up a Project Environment¶

Create a project structure:

my_project/
  myenv/
  src/
    main.py
  requirements.txt
  README.md

Create requirements.txt:

requests==2.28.0
python-dotenv==0.20.0

Create src/main.py:

import requests
from dotenv import load_dotenv
import os

load_dotenv()

# Example: fetch data from an API
response = requests.get("https://api.github.com")
print(f"Status: {response.status_code}")
print(f"Headers: {response.headers}")

Set up the environment:

# Create virtual environment
python -m venv myenv

# Activate it
myenv\Scripts\activate  # Windows
source myenv/bin/activate  # macOS/Linux

# Install dependencies
pip install -r requirements.txt

# Run the script
python src/main.py

Exercise 6: Manage Development Dependencies¶

Create requirements-dev.txt:

# Production dependencies
requests==2.28.0

# Development dependencies
pytest==7.1.0
black==22.6.0
flake8==4.0.1

Install development dependencies:

pip install -r requirements-dev.txt

Use the tools:

# Format code with black
black src/

# Check code style with flake8
flake8 src/

# Run tests with pytest
pytest tests/

Exercise 7: Troubleshoot Environment Issues¶

Create a test script test_env.py:

import sys
import os

print(f"Python version: {sys.version}")
print(f"Python executable: {sys.executable}")
print(f"Virtual environment: {sys.prefix}")
print(f"Python path: {sys.path}")

# Check if packages are installed
try:
    import requests
    print("✓ requests is installed")
except ImportError:
    print("✗ requests is NOT installed")

try:
    import flask
    print("✓ flask is installed")
except ImportError:
    print("✗ flask is NOT installed")

# List installed packages
import pkg_resources
print("\nInstalled packages:")
for dist in pkg_resources.working_set:
    print(f"  {dist.project_name}=={dist.version}")

Run it to diagnose environment issues:

python test_env.py

Challenge Exercises¶

Challenge 1: Create Multiple Environments¶

Create separate environments for different projects:

# Project 1: Web development
python -m venv web_env
web_env\Scripts\activate  # Windows
pip install flask flask-sqlalchemy

# Project 2: Data analysis
python -m venv data_env
data_env\Scripts\activate  # Windows
pip install pandas numpy matplotlib

# Project 3: Testing
python -m venv test_env
test_env\Scripts\activate  # Windows
pip install pytest pytest-cov

Switch between environments by activating/deactivating.

Challenge 2: Upgrade and Downgrade Packages¶

# Check for outdated packages
pip list --outdated

# Upgrade a specific package
pip install --upgrade requests

# Upgrade all packages
pip install --upgrade -r requirements.txt

# Downgrade a package
pip install requests==2.27.0

# Pin a package to a specific version
pip install requests==2.28.0 --force-reinstall

Challenge 3: Create a Project Template¶

Create a template directory structure:

project_template/
  myenv/
  src/
    __init__.py
    main.py
  tests/
    __init__.py
    test_main.py
  requirements.txt
  requirements-dev.txt
  README.md
  .gitignore

Create .gitignore:

myenv/
__pycache__/
*.pyc
.pytest_cache/
.coverage
dist/
build/
*.egg-info/

Create README.md:

# My Project

## Setup

1. Create virtual environment:
   ```bash
   python -m venv myenv
   ```

2. Activate it:
   ```bash
   myenv\Scripts\activate  # Windows
   source myenv/bin/activate  # macOS/Linux
   ```

3. Install dependencies:
   ```bash
   pip install -r requirements.txt
   ```

## Development

Install dev dependencies:
```bash
pip install -r requirements-dev.txt

Run tests:

pytest

Format code:

black src/

```

Hints¶

"python: command not found" → Python may not be in your PATH. Try python3 instead, or reinstall Python.

"No module named X" → The package is not installed. Use pip install X or check that the virtual environment is activated.

Virtual environment not activating → Check the path and ensure you're using the correct activation script for your OS.

Conflicting dependencies → Use pip install --upgrade pip and check for version conflicts with pip check.

What to Review If You Get Stuck¶

Virtual environments → Handbook section 2.1
pip basics → Handbook section 2.2
requirements.txt → Handbook section 2.3
Managing dependencies → Handbook section 2.4
Troubleshooting → Handbook section 2.5

Key Takeaways¶

After completing these exercises, you should be able to:

Create and activate virtual environments
Install and manage packages with pip
Create and use requirements.txt files
Manage development dependencies
Troubleshoot environment issues
Use multiple environments for different projects
Upgrade and downgrade packages
Set up project templates