Accessing JSON data in Flask - Mini Project: Build & Apply

Accessing JSON data in Flask

📖 Scenario: You are building a simple Flask web app that receives JSON data from a client. The JSON contains user information like name and age.

🎯 Goal: Learn how to access JSON data sent in a POST request in Flask and extract specific fields.

📋 What You'll Learn

Create a Flask app with a route to accept POST requests

Access JSON data from the request

Extract specific fields from the JSON

Return a response using the extracted data

💡 Why This Matters

🌍 Real World

Many web apps receive data from clients in JSON format. Knowing how to access and use this data is essential for building APIs.

💼 Career

Backend developers often work with JSON data in Flask or other frameworks to build REST APIs and handle client requests.

1

Set up Flask app and route

Import Flask and request from flask. Create a Flask app called app. Define a route /user that accepts POST requests.

Flask

from flask import Flask, request

app = Flask(__name__)

@app.route('/user', methods=['POST'])
def user():
    # Your code here

Need a hint?

Use @app.route decorator with methods=['POST'] to create the route.

2

Access JSON data from the request

Inside the user function, create a variable called data and assign it the JSON data from the request using request.get_json().

Flask

from flask import Flask, request

app = Flask(__name__)

@app.route('/user', methods=['POST'])
def user():
    data = request.get_json()
    # Your code here

Need a hint?

Use request.get_json() to get the JSON data sent in the POST request.

3

Extract fields from JSON data

From the data dictionary, extract the values for name and age into variables called name and age.

Flask

from flask import Flask, request

app = Flask(__name__)

@app.route('/user', methods=['POST'])
def user():
    data = request.get_json()
    name = data['name']
    age = data['age']
    # Your code here

Need a hint?

Use dictionary key access like data['name'] to get values.

4

Return a response using extracted data

Return a string response that says "User {name} is {age} years old." using an f-string with the variables name and age.

Flask

from flask import Flask, request

app = Flask(__name__)

@app.route('/user', methods=['POST'])
def user():
    data = request.get_json()
    name = data['name']
    age = data['age']
    return f"User {name} is {age} years old."
    # Your code here

Need a hint?

Use an f-string to format the response string with name and age.