File size limits in Flask - Mini Project: Build & Apply

File Size Limits in Flask

📖 Scenario: You are building a simple Flask web app that allows users to upload files. To keep the server safe and efficient, you want to limit the size of files users can upload.

🎯 Goal: Create a Flask app that sets a file size limit of 1 megabyte (1MB) and handles file uploads with this limit enforced.

📋 What You'll Learn

Create a Flask app instance

Set the maximum allowed file size to 1MB using Flask configuration

Write a route to accept file uploads

Add error handling for files that exceed the size limit

💡 Why This Matters

🌍 Real World

Limiting file upload size is important to protect servers from overload and abuse in real web applications.

💼 Career

Understanding how to configure Flask apps and handle file uploads is a common task for backend web developers.

1

Create the Flask app instance

Create a Flask app instance called app using Flask(__name__).

Flask

# Create the Flask app instance
# Your code here

Need a hint?

Use Flask(__name__) to create the app instance.

2

Set the maximum file size limit

Set the Flask configuration variable MAX_CONTENT_LENGTH to 1 * 1024 * 1024 (which is 1MB) on the app.config dictionary.

Flask

from flask import Flask

app = Flask(__name__)
# Set max file size limit to 1MB
# Your code here

Need a hint?

Use app.config['MAX_CONTENT_LENGTH'] = 1 * 1024 * 1024 to set the limit.

3

Create a file upload route

Create a route /upload that accepts POST requests. Inside the route function called upload_file, get the uploaded file from request.files['file'] and return the string 'File uploaded'.

Flask

from flask import Flask, request

app = Flask(__name__)
app.config['MAX_CONTENT_LENGTH'] = 1 * 1024 * 1024

# Create /upload route to accept POST and get uploaded file
# Your code here

Need a hint?

Use @app.route('/upload', methods=['POST']) and get the file with request.files['file'].

4

Add error handling for large files

Import RequestEntityTooLarge from werkzeug.exceptions. Add an error handler for RequestEntityTooLarge on app.errorhandler that returns the string 'File too large' with status code 413.

Flask

from flask import Flask, request
from werkzeug.exceptions import RequestEntityTooLarge

app = Flask(__name__)
app.config['MAX_CONTENT_LENGTH'] = 1 * 1024 * 1024

@app.route('/upload', methods=['POST'])
def upload_file():
    file = request.files['file']
    return 'File uploaded'

# Add error handler for RequestEntityTooLarge
# Your code here

Need a hint?

Use @app.errorhandler(RequestEntityTooLarge) to catch large file errors.