Serving uploaded files in Flask - Mini Project: Build & Apply

Serving Uploaded Files with Flask

📖 Scenario: You are building a simple Flask web app where users can upload files. After uploading, users should be able to access and download their files from the server.

🎯 Goal: Build a Flask app that serves uploaded files from a specific folder so users can download them by visiting a URL.

📋 What You'll Learn

Create a Flask app with an upload folder path

Set a configuration variable for the upload folder

Write a route to serve files from the upload folder

Use Flask's send_from_directory function to serve files

💡 Why This Matters

🌍 Real World

Web apps often let users upload files like images or documents. Serving these files back to users requires safely sending files from a server folder.

💼 Career

Knowing how to serve uploaded files is essential for backend web developers working with Flask or similar frameworks.

1

Set up the upload folder path

Create a variable called UPLOAD_FOLDER and set it to the string 'uploads'.

Flask

# Your code here

Need a hint?

This variable will tell Flask where to find the uploaded files.

2

Configure the Flask app to use the upload folder

Add a line to set app.config['UPLOAD_FOLDER'] equal to the variable UPLOAD_FOLDER.

Flask

UPLOAD_FOLDER = 'uploads'
# Your code here

Need a hint?

This tells Flask where to look for uploaded files when serving them.

3

Create a route to serve uploaded files

Write a Flask route with the URL pattern /uploads/<filename> that uses a function named uploaded_file with a parameter filename.

Flask

from flask import Flask

app = Flask(__name__)
UPLOAD_FOLDER = 'uploads'
app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER

# Your code here

Need a hint?

This route will handle requests to get files by their filename.

4

Serve the file using send_from_directory

Inside the uploaded_file function, return the result of calling send_from_directory with app.config['UPLOAD_FOLDER'] and filename as arguments.

Flask

from flask import Flask, send_from_directory

app = Flask(__name__)
UPLOAD_FOLDER = 'uploads'
app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER

@app.route('/uploads/')
def uploaded_file(filename):
    # Your code here

Need a hint?

This function sends the requested file from the upload folder to the user.