Building a Weather Forecasting Application with Python

juillet 23, 2024

Building a Weather Forecasting Application with Python

Python is a versatile programming language that's great for a wide range of projects, from simple scripts to complex applications. Today, we're going to dive into a fun and practical Python project: creating a weather forecasting application. This project will teach you how to work with APIs, handle JSON data, and build a user-friendly interface using a simple web framework. Let's get started!

Project Overview

Our goal is to build a weather forecasting application that allows users to input a city name and get the current weather details for that city. We'll use the OpenWeatherMap API to fetch weather data and Flask to create a web interface.

Prerequisites

Before we begin, make sure you have the following:

- Python installed on your machine (preferably Python 3.7+)

- Basic knowledge of Python programming

- An API key from OpenWeatherMap (sign up for free at their [website](https://openweathermap.org/))

#### Step 1: Setting Up the Environment

First, let's set up our project environment. We'll create a new directory for our project and set up a virtual environment.

```bash

$mkdir weather_app

$cd weather_app

$python -m venv venv

$source venv/bin/activate  # On Windows use `venv\Scripts\activate`

```

Next, we'll install the necessary Python packages. We'll need `Flask` for our web framework and `requests` to handle our API calls.

```bash

$pip install Flask requests

```

#### Step 2: Getting Weather Data

Let's start by writing a function to fetch weather data from the OpenWeatherMap API. Create a new file called `weather.py`.

```python

    import requests

    API_KEY = 'your_api_key'  # Replace with your actual API key

    def get_weather(city):

        url = f'http://api.openweathermap.org/data/2.5/weather?q={city}&appid={API_KEY}&units=metric'

        response = requests.get(url)

        data = response.json()

        if response.status_code == 200:

            weather = {

                'city': data['name'],

                'temperature': data['main']['temp'],

                'description': data['weather'][0]['description'],

                'icon': data['weather'][0]['icon'],

            }

            return weather

        else:

            return None

```

This function takes a city name as input, makes a request to the OpenWeatherMap API, and returns a dictionary with the city's weather details.

#### Step 3: Creating the Flask Application

Now, let's create the Flask web application. Create a new file called `app.py`.

```python

from flask import Flask, render_template, request

from weather import get_weather

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])

def index():

    if request.method == 'POST':

        city = request.form.get('city')

        weather = get_weather(city)

        if weather:

            return render_template('index.html', weather=weather)

        else:

            return render_template('index.html', error='City not found')

    return render_template('index.html')

if __name__ == '__main__':

    app.run(debug=True)

```

This code sets up a basic Flask application with a single route. When a user submits a city name via a form, the app fetches the weather data and displays it.

#### Step 4: Creating the HTML Template

Let's create the HTML template for our application. Create a new directory called `templates` and inside it, create a file called `index.html`.

```html

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <title>Weather App</title>

</head>

<body>

    <h1>Weather Forecast</h1>

    <form method="POST">

        <input type="text" name="city" placeholder="Enter city name" required>

        <button type="submit">Get Weather</button>

    </form>

    {% if weather %}

        <h2>Weather in {{ weather.city }}</h2>

        <p>Temperature: {{ weather.temperature }}°C</p>

        <p>Description: {{ weather.description }}</p>

        <img src="http://openweathermap.org/img/wn/{{ weather.icon }}@2x.png" alt="Weather icon">

    {% elif error %}

        <p>{{ error }}</p>

    {% endif %}

</body>

</html>

```

This simple template includes a form for inputting a city name and displays the weather information if available.

#### Step 5: Running the Application

To run the application, simply execute the `app.py` file.

```bash

$python app.py

```

Navigate to `http://127.0.0.1:5000/` in your web browser, and you should see your weather application in action. Enter a city name, and the app will display the current weather for that city.

#### Conclusion

Congratulations! You've built a weather forecasting application using Python, Flask, and the OpenWeatherMap API. This project is a great example of how you can combine different technologies to create a useful and interactive application.

From here, you can expand the project by adding more features, such as a five-day forecast, historical weather data, or even integrating maps. The possibilities are endless, and each addition will help you learn more about Python and web development. Happy coding!

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