File upload forms in Flask - Cheat Sheet & Quick Revision

Recall & Review

beginner

What HTML element is used to allow users to select files for upload in a form?

The <input> element with type="file" is used to let users pick files to upload.

beginner

In Flask, which object holds the uploaded file data after a form submission?

Flask stores uploaded files in the request.files dictionary, accessible by the file input's name.

beginner

Why must the form tag include enctype="multipart/form-data" when uploading files?

This encoding type tells the browser to send files and form data properly so the server can read the files.

intermediate

How do you save an uploaded file to the server in Flask?

Use the save() method on the uploaded file object, providing a safe file path to store it.

intermediate

What is a common security practice when saving uploaded files in Flask?

Use werkzeug.utils.secure_filename() to clean the filename and avoid unsafe characters or paths.

Which attribute must a form have to upload files correctly?

A type="file"

B method="get"

C action="upload"

D enctype="multipart/form-data"

The form must have enctype="multipart/form-data" to send files properly.

In Flask, where do uploaded files appear after form submission?

A request.files

B request.args

C request.form

D request.data

Uploaded files are stored in request.files, not in form or args.

What method do you call on an uploaded file object to save it?

A write()

B save()

C store()

D upload()

The save() method saves the uploaded file to disk.

Which function helps secure filenames before saving in Flask?

A secure_filename()

B sanitize_path()

C clean_name()

D safe_path()

secure_filename() from werkzeug.utils cleans filenames safely.

What input type allows users to select multiple files at once?

A <input type="files">

B <input type="upload">

C <input type="file" multiple>

D <input type="file" multiple="false">

Adding the multiple attribute lets users pick several files.

Explain the steps to create a file upload form in Flask and handle the uploaded file safely.

Think about both the HTML form setup and the Flask backend handling.

Why is it important to use secure_filename() when saving uploaded files in Flask?

Consider what could happen if filenames are not cleaned.