Parameter type converters (int, float, path) in Flask - Mini Project: Build & Apply

Using Parameter Type Converters in Flask Routes

📖 Scenario: You are building a simple Flask web app that shows different pages based on URL parameters. You want to make sure the parameters are the right type so your app works smoothly.

🎯 Goal: Create Flask routes that use parameter type converters int, float, and path to handle URL parameters correctly.

📋 What You'll Learn

Create a Flask app instance named app

Add a route /item/<int:item_id> that accepts only integer item_id

Add a route /price/<float:price> that accepts only float price

Add a route /file/<path:filepath> that accepts a path string filepath

💡 Why This Matters

🌍 Real World

Web developers often need to get data from URLs and ensure it is the right type before using it. Flask's parameter type converters make this easy and reliable.

💼 Career

Understanding how to use Flask routes with typed parameters is essential for backend web development jobs that use Python and Flask frameworks.

1

Set up the Flask app and integer route

Import Flask from flask and create a Flask app instance called app. Then add a route /item/<int:item_id> that accepts an integer parameter called item_id. Inside the route function show_item, return a string showing the item ID using an f-string.

Flask

from flask import Flask

app = Flask(__name__)

# Create route /item/ below
# Your code here

Need a hint?

Use @app.route('/item/<int:item_id>') to specify the integer parameter in the URL.

2

Add a route with a float parameter

Add a new route /price/<float:price> that accepts a float parameter called price. Define a function show_price that returns a string showing the price with two decimal places using an f-string.

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/item/')
def show_item(item_id):
    return f"Item ID is {item_id}"

# Add route /price/ below
# Your code here

Need a hint?

Use @app.route('/price/<float:price>') and format the float with {price:.2f} in the f-string.

3

Add a route with a path parameter

Add a route /file/<path:filepath> that accepts a path parameter called filepath. Define a function show_file that returns a string showing the file path.

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/item/')
def show_item(item_id):
    return f"Item ID is {item_id}"

@app.route('/price/')
def show_price(price):
    return f"Price is ${price:.2f}"

# Add route /file/ below
# Your code here

Need a hint?

Use @app.route('/file/<path:filepath>') to accept a path parameter.

4

Add the app run command

Add the code to run the Flask app only if the script is run directly. Use app.run(debug=True) inside the if __name__ == '__main__': block.

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/item/')
def show_item(item_id):
    return f"Item ID is {item_id}"

@app.route('/price/')
def show_price(price):
    return f"Price is ${price:.2f}"

@app.route('/file/')
def show_file(filepath):
    return f"File path is {filepath}"

# Add the app run command below
# Your code here

Need a hint?

Use the standard Python check if __name__ == '__main__': to run the app.