exercise1

Simple Flask Server Application

Table of Contents

• Introduction
• Prerequisites
• Navigate to the Application Directory
• Install Flask
• Code Explanation
• Run the Application
• Final Objective

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Introduction

In this class, you will learn how to run a simple server application using Python and Flask.

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Prerequisites

Ensure you have Python installed on your system. You can verify this by running:

python3 --version

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Navigate to the Application Directory

Navigate to the exercise1 directory where the application files are located:

cd sre-abc-training/exercises/exercise1

This ensures you are in the correct directory to execute the application.

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Install Flask

Flask is a lightweight WSGI web application framework in Python. To install Flask, use pip:

pip3 install Flask

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Code Explanation

The code creates a Flask application with two main endpoints:

1. A root endpoint (/) that returns a "Hello, World!" message.
2. An endpoint for retrieving store information (/store).

Code Breakdown

from flask import Flask, request

app = Flask(__name__)

• Importing Flask: This imports the Flask class from the flask library.
• Initializing the App: app = Flask(__name__) creates an instance of the Flask application.

@app.route('/')
def hello_world():
    return 'Hello, World!'

• Root Route (/): This is a basic endpoint that listens on the root (/) URL. When accessed, it returns the plain text message "Hello, World!".

stores = [
    {
        "name": "My Store",
        "items": [
            {
                "name": "Chair",
                "price": 15.99
            }
        ]
    }
]

• Stores Data: This is a simple data structure representing a store. It contains an array of items, with each item represented by its name and price.

@app.get('/store') # 'http://127.0.0.1:5000/store'
def get_stores():
    return {"stores": stores}

• Get Stores Route (/store): This endpoint returns a JSON object containing all stores. The @app.get('/store') decorator defines this route, making it accessible via a GET request.

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

• Running the App: This conditional statement checks if the script is run directly (rather than imported as a module). If it is, the Flask application starts up, listening on all network interfaces (0.0.0.0) at port 5000.

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Run the Application

To run the Flask application, execute the following commands from the exercise1 directory:

python3 app.py

Once the application is running, you can open your browser and visit the following URLs:

• Root Route: http://127.0.0.1:5000/
• Stores Route: http://127.0.0.1:5000/store

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Final Objective

At the end of this exercise, you should accomplish the following:

[!IMPORTANT]
Once the application is running, open your web browser and go to http://127.0.0.1:5000/. You should see the text "Hello, World!" displayed.

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