Building REST APIs with Flask

Name: Building REST APIs with Flask
Availability: InStock
Author: Revochamp

What is Flask?

Flask is a 'micro' web framework for Python. It is called micro because it does not require particular tools or libraries. It has no database abstraction layer, form validation, or any other components where pre-existing third-party libraries provide common functions. This makes it incredibly flexible and an excellent choice for building lightweight REST APIs or microservices.

Setting Up a Simple Flask API

To create an API endpoint in Flask, you define a function and decorate it with @app.route(). You specify the URL path and the allowed HTTP methods.

PythonRead-only

from flask import Flask, jsonify, request

app = Flask(__name__)

# A simple in-memory data store
items = [{"id": 1, "name": "Item One"}]

@app.route('/items', methods=['GET'])
def get_items():
    return jsonify(items)

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

from flask import Flask, jsonify, request

app = Flask(__name__)

# A simple in-memory data store
items = [{"id": 1, "name": "Item One"}]

@app.route('/items', methods=['GET'])
def get_items():
    return jsonify(items)

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

Handling POST Requests

When building a REST API, you often need to receive data from the client. In Flask, you use the request object to access the JSON payload sent in the body of a POST request.

PythonRead-only

@app.route('/items', methods=['POST'])
def add_item():
    new_item = request.get_json()
    items.append(new_item)
    return jsonify(new_item), 201

@app.route('/items', methods=['POST'])
def add_item():
    new_item = request.get_json()
    items.append(new_item)
    return jsonify(new_item), 201

Dynamic Routing (URL Parameters)

You can capture values from the URL using angle brackets <>. This is essential for building endpoints that act on specific resources, like fetching a single user by their ID.

PythonRead-only

@app.route('/items/<int:item_id>', methods=['GET'])
def get_item(item_id):
    item = next((i for i in items if i['id'] == item_id), None)
    if item:
        return jsonify(item)
    return jsonify({"error": "Item not found"}), 404

@app.route('/items/<int:item_id>', methods=['GET'])
def get_item(item_id):
    item = next((i for i in items if i['id'] == item_id), None)
    if item:
        return jsonify(item)
    return jsonify({"error": "Item not found"}), 404

Flask vs. FastAPI for REST

Feature	Flask	FastAPI
Style	WSGI (Synchronous)	ASGI (Asynchronous)
Data Validation	Manual	Automatic (via Pydantic)
Speed	Fast	Very Fast
Documentation	Requires extensions	Automatic Swagger UI
Flexibility	Extremely High	High (but opinionated)

Test Your Knowledge

of 3

Which decorator is used to define a route in Flask?

@app.path()

@app.route()

@flask.api()

@route.add()

of 3

Which Flask object is used to access incoming request data like JSON or form values?

response

payload

request

data

of 3

What is the purpose of the 'debug=True' flag in app.run()?

It makes the API faster

It enables a debugger and automatically reloads the server on code changes

It hides errors from the user

It prepares the app for production deployment

Frequently Asked Questions

What is 'jsonify' in Flask?

It is a helper function that turns a Python dictionary or list into a JSON response object and automatically sets the 'Content-Type' header to 'application/json'.

How do I handle CORS in Flask?

If your Flutter or React app is on a different domain, you'll need the 'Flask-CORS' extension to allow the browser to make requests to your API.

Is Flask suitable for production?

Yes! While the built-in server is for development only, Flask apps are production-ready when deployed behind a robust WSGI server like Gunicorn or uWSGI.

from flask import Flask, jsonify, request app = Flask(__name__) # A simple in-memory data store items = [{"id": 1, "name": "Item One"}] @app.route('/items', methods=['GET']) def get_items(): return jsonify(items) if __name__ == '__main__': app.run(debug=True)

@app.route('/items/<int:item_id>', methods=['GET']) def get_item(item_id): item = next((i for i in items if i['id'] == item_id), None) if item: return jsonify(item) return jsonify({"error": "Item not found"}), 404

Feature

Flask

FastAPI

Style

WSGI (Synchronous)

ASGI (Asynchronous)

Data Validation

Manual

Automatic (via Pydantic)

Speed

Fast

Very Fast

Documentation

Requires extensions

Automatic Swagger UI

Flexibility

Extremely High

High (but opinionated)

Test Your Knowledge

of 3

Which decorator is used to define a route in Flask?

@app.path()

@app.route()

@flask.api()

@route.add()

of 3

Which Flask object is used to access incoming request data like JSON or form values?

response

payload

request

data

of 3

What is the purpose of the 'debug=True' flag in app.run()?

It makes the API faster

It enables a debugger and automatically reloads the server on code changes

It hides errors from the user

It prepares the app for production deployment

Frequently Asked Questions

What is 'jsonify' in Flask?

It is a helper function that turns a Python dictionary or list into a JSON response object and automatically sets the 'Content-Type' header to 'application/json'.

How do I handle CORS in Flask?

If your Flutter or React app is on a different domain, you'll need the 'Flask-CORS' extension to allow the browser to make requests to your API.

Is Flask suitable for production?

Yes! While the built-in server is for development only, Flask apps are production-ready when deployed behind a robust WSGI server like Gunicorn or uWSGI.

Building REST APIs with Flask

What is Flask?

Setting Up a Simple Flask API

Handling POST Requests

Dynamic Routing (URL Parameters)

Flask vs. FastAPI for REST

Test Your Knowledge

Frequently Asked Questions

Need help?

Building REST APIs with Flask

Building REST APIs with Flask

What is Flask?

Setting Up a Simple Flask API

Handling POST Requests

Dynamic Routing (URL Parameters)

Flask vs. FastAPI for REST

Test Your Knowledge

Frequently Asked Questions

Need help?