File uploads handling in Flask - Cheat Sheet & Quick Revision

Recall & Review

beginner

What Flask object is used to access uploaded files in a request?

The request.files object holds all uploaded files in a Flask request. You can access files by their form field names.

beginner

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

Use the save() method on the uploaded file object, passing the destination path as a string, e.g., file.save('/path/to/save').

intermediate

Why should you check the file extension or content type before saving an uploaded file?

To avoid security risks like uploading harmful files. Checking extensions or MIME types helps ensure only allowed file types are saved.

intermediate

What Flask configuration helps limit the maximum size of uploaded files?

The MAX_CONTENT_LENGTH configuration sets the maximum size (in bytes) for incoming request data, preventing very large uploads.

intermediate

How can you safely generate a filename for saving an uploaded file in Flask?

Use werkzeug.utils.secure_filename() to clean the filename, removing unsafe characters and preventing directory traversal attacks.

Which Flask object holds uploaded files from a form?

A request.files

B request.form

C request.data

D request.args

request.files contains uploaded files. request.form has text fields.

What method do you call to save an uploaded file in Flask?

A save()

B upload()

C store()

D write()

The save() method saves the file to disk.

Which Flask config limits upload size?

A MAX_UPLOAD_SIZE

B UPLOAD_LIMIT

C MAX_FILE_SIZE

D MAX_CONTENT_LENGTH

MAX_CONTENT_LENGTH sets max request size.

Why use secure_filename() on uploaded files?

A To compress the file

B To encrypt the file

C To clean the filename for safety

D To rename the file randomly

secure_filename() removes unsafe characters from filenames.

What happens if an uploaded file exceeds MAX_CONTENT_LENGTH?

A File uploads normally

B Flask raises a RequestEntityTooLarge error

C File is truncated

D File is saved partially

Flask blocks the request and raises an error if size is too big.

Explain the steps to handle a file upload in Flask from receiving the file to saving it safely.

Think about how to get the file, check it, and save it securely.

Describe how Flask's MAX_CONTENT_LENGTH setting helps with file uploads.

Consider why limiting upload size is important.