Serving uploaded files in Flask - Cheat Sheet & Quick Revision

Recall & Review

beginner

What Flask function is commonly used to serve uploaded files to users?

The send_from_directory() function is used to safely serve uploaded files from a specific folder to users.

intermediate

Why should you avoid serving uploaded files directly from the upload folder without precautions?

Serving files directly can expose sensitive files or allow execution of harmful files. Using send_from_directory() helps control access and prevents security risks.

beginner

How do you specify the folder from which Flask serves uploaded files?

You pass the folder path as the first argument to send_from_directory(), for example: send_from_directory('uploads', filename).

beginner

What HTTP method is typically used when a user requests to download or view an uploaded file?

The GET method is used because the user is requesting to retrieve and view or download the file.

beginner

What is a simple Flask route example to serve an uploaded file named filename from the uploads folder?

<pre>from flask import send_from_directory

@app.route('/uploads/&lt;filename&gt;')
def uploaded_file(filename):
    return send_from_directory('uploads', filename)</pre>

Which Flask function should you use to serve a file from a specific folder?

A redirect()

B render_template()

C send_from_directory()

D url_for()

send_from_directory() is designed to serve files from a folder safely.

What is the main security reason to use send_from_directory() instead of serving files directly?

A It compresses files automatically

B It prevents unauthorized file access

C It changes file names

D It encrypts files

send_from_directory() helps prevent unauthorized access by controlling which files are served.

In Flask, which HTTP method is used to request an uploaded file for download or viewing?

A GET

B DELETE

C PUT

D POST

GET is used to retrieve resources like files.

What argument do you pass first to send_from_directory()?

A The filename

B The file size

C The file extension

D The folder path

The first argument is the folder path where the file is located.

Which of these is a correct Flask route to serve a file named filename from the uploads folder?

A @app.route('/uploads/<filename>') def file(filename): return send_from_directory('uploads', filename)

B @app.route('/uploads') def file(): return send_from_directory('uploads')

C @app.route('/uploads/<filename>') def file(filename): return render_template(filename)

D @app.route('/uploads/<filename>') def file(filename): return redirect('uploads/' + filename)

Option A correctly uses send_from_directory() with the folder and filename.

Explain how to serve an uploaded file safely in Flask and why it is important.

Think about how Flask controls file access and protects the server.

Describe the steps to create a Flask route that allows users to download files they uploaded.

Focus on the route setup and the function used to send files.