Python Full Stack Web Developer Course

Practical Exercise: Setting Up a Python Project Environment

Let's put what we've learned into practice with a hands-on exercise. We'll create a complete Python project environment from scratch.

Exercise Goals

By the end of this exercise, you will have:

• Created a new Python project with a proper directory structure
• Set up a virtual environment
• Installed project dependencies
• Created a requirements file
• Written a simple Python script to verify everything works

Step 1: Create Project Directory Structure

# Create main project directory
mkdir weather_app
cd weather_app

# Create subdirectories
mkdir src tests docs
            

Step 2: Create and Activate a Virtual Environment

# Create virtual environment
python -m venv .venv

# Activate the environment
# On Windows:
.venv\Scripts\activate

# On macOS/Linux:
source .venv/bin/activate

# Verify activation (you should see the environment name in your prompt)
            

Step 3: Install Dependencies

# Install required packages
pip install requests pytest

# Create requirements file
pip freeze > requirements.txt
            

Step 4: Create a Simple Python Script

Create a file src/weather.py with the following content:

import requests

def get_weather(city, api_key="demo"):
    """
    Get current weather for a city using the OpenWeatherMap API.
    
    Args:
        city (str): Name of the city
        api_key (str): OpenWeatherMap API key (default: "demo" for testing)
        
    Returns:
        dict: Weather data if successful, None otherwise
    """
    base_url = "https://api.openweathermap.org/data/2.5/weather"
    params = {
        "q": city,
        "appid": api_key,
        "units": "metric"
    }
    
    try:
        response = requests.get(base_url, params=params)
        response.raise_for_status()  # Raise exception for HTTP errors
        return response.json()
    except requests.exceptions.RequestException as e:
        print(f"Error fetching weather data: {e}")
        return None

def format_weather(weather_data):
    """
    Format weather data into a readable string.
    
    Args:
        weather_data (dict): Weather data from the API
        
    Returns:
        str: Formatted weather information
    """
    if not weather_data:
        return "No weather data available."
    
    try:
        city = weather_data["name"]
        country = weather_data["sys"]["country"]
        temp = weather_data["main"]["temp"]
        description = weather_data["weather"][0]["description"]
        humidity = weather_data["main"]["humidity"]
        
        return f"Weather in {city}, {country}:\n" \
               f"Temperature: {temp}°C\n" \
               f"Conditions: {description}\n" \
               f"Humidity: {humidity}%"
    except KeyError:
        return "Error: Weather data format is unexpected."

def main():
    """Main function to run the weather app."""
    city = input("Enter city name: ")
    weather_data = get_weather(city)
    weather_info = format_weather(weather_data)
    print("\n" + weather_info)

if __name__ == "__main__":
    main()
            

Step 5: Create a Simple Test

Create a file tests/test_weather.py with the following content:

import pytest
from src.weather import format_weather

def test_format_weather_valid_data():
    # Sample weather data
    weather_data = {
        "name": "London",
        "sys": {"country": "GB"},
        "main": {"temp": 15.5, "humidity": 76},
        "weather": [{"description": "cloudy"}]
    }
    
    result = format_weather(weather_data)
    
    assert "London, GB" in result
    assert "15.5°C" in result
    assert "cloudy" in result
    assert "76%" in result

def test_format_weather_no_data():
    result = format_weather(None)
    assert result == "No weather data available."

def test_format_weather_invalid_data():
    result = format_weather({})
    assert "Error" in result
            

Step 6: Create a README File

Create a file README.md with information about your project:

# Weather App

A simple command-line weather application that fetches current weather data.

## Setup

1. Create and activate a virtual environment:
   ```
   python -m venv .venv
   source .venv/bin/activate  # On Windows: .venv\Scripts\activate
   ```

2. Install dependencies:
   ```
   pip install -r requirements.txt
   ```

## Usage

Run the application:
```
python src/weather.py
```

## Running Tests

Run tests with pytest:
```
pytest tests/
```

## Project Structure

- `src/`: Source code
- `tests/`: Test files
- `docs/`: Documentation
- `.venv/`: Virtual environment (not included in repository)
            

Step 7: Verify Everything Works

# Run the tests
pytest tests/

# Run the application
python src/weather.py
            

Step 8: Clean Up (Optional)

When you're done, you can deactivate the virtual environment:

deactivate
            

This exercise demonstrates a complete Python project setup using a virtual environment. The structure follows best practices and includes basic project components: a functional script, tests, requirements, and documentation.