FlaskHow-ToBeginner · 3 min read

How to Create Route in Flask: Simple Guide with Examples

In Flask, you create a route by using the @app.route() decorator above a function that returns the response for that URL. This connects a URL path to a Python function, so when users visit that path, Flask runs the function and shows its output.

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Syntax

The basic syntax to create a route in Flask uses the @app.route() decorator followed by a function. The decorator takes the URL path as a string. The function below it defines what to show when that URL is visited.

@app.route('/path'): Defines the URL path to listen to.
def function_name(): The function that runs when the path is accessed.
return: Sends the response back to the browser.

python

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return 'Hello, Flask!'

if __name__ == '__main__':
    app.run()

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Example

This example shows a Flask app with two routes: the home page at / and an about page at /about. Each route returns a simple text message.

python

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return 'Welcome to the Home Page!'

@app.route('/about')
def about():
    return 'This is the About Page.'

if __name__ == '__main__':
    app.run()

Output

Running on http://127.0.0.1:5000/ (Press CTRL+C to quit) Visiting http://127.0.0.1:5000/ shows: Welcome to the Home Page! Visiting http://127.0.0.1:5000/about shows: This is the About Page.

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Common Pitfalls

Common mistakes when creating routes in Flask include:

Forgetting the @app.route() decorator above the function.
Using the same route for multiple functions, which causes conflicts.
Not returning a response from the function, which leads to errors.
Running the app without the if __name__ == '__main__' guard in development.

python

from flask import Flask
app = Flask(__name__)

# Wrong: Missing decorator
# def missing_route():
#     return 'No route here'

# Right:
@app.route('/correct')
def correct_route():
    return 'This route works'

if __name__ == '__main__':
    app.run()

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Quick Reference

Concept	Description	Example
@app.route('/path')	Defines the URL path for the route	@app.route('/home')
Function below decorator	Runs when the route is accessed	def home(): return 'Hi'
Return value	Response sent to the browser	return 'Hello'
Running app	Starts the Flask server	app.run()

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Key Takeaways

Use @app.route('/path') decorator to link a URL to a function.

Always return a response from the route function.

Avoid duplicate routes to prevent conflicts.

Use if __name__ == '__main__' to run the app safely in development.

Routes define what users see when they visit specific URLs.