Allowed file types validation in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define allowed file extensions as a set.

Flask

ALLOWED_EXTENSIONS = [1]

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A['png', 'jpg', 'jpeg', 'gif']

B('png', 'jpg', 'jpeg', 'gif')

C"png, jpg, jpeg, gif"

D{'png', 'jpg', 'jpeg', 'gif'}

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list instead of a set slows down membership checks.

Using a string instead of a collection causes errors.

Allowed file extensions should be stored in a set for fast lookup.

2fill in blank

medium

Complete the function to check if a filename has an allowed extension.

Flask

def allowed_file(filename):
    return '.' in filename and filename.rsplit('.', 1)[1].[1]() in ALLOWED_EXTENSIONS

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Alower

Bupper

Cstartswith

Dendswith

Attempts:

3 left

💡 Hint

Common Mistakes

Using startswith or endswith instead of lower.

Not converting to lowercase causes case sensitivity issues.

We convert the extension to lowercase before checking to allow case-insensitive matching.

3fill in blank

hard

Fix the error in the file upload route to validate file type correctly.

Flask

from flask import request, redirect, url_for

@app.route('/upload', methods=['POST'])
def upload_file():
    file = request.files.get('file')
    if file and allowed_file(file.filename):
        filename = secure_filename(file.filename)
        file.save(os.path.join(app.config['UPLOAD_FOLDER'], [1]))
        return redirect(url_for('uploaded_file', filename=filename))
    return 'Invalid file type', 400

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Afilename

Bfile.filename

Cfile

Drequest.filename

Attempts:

3 left

💡 Hint

Common Mistakes

Using file.filename directly without securing it.

Using file or request.filename which are incorrect.

The variable filename holds the safe filename to save.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension filtering allowed files and mapping to their extensions.

Flask

files = ['image.png', 'doc.pdf', 'photo.jpg']
allowed_files = {f: f.[1]('.', 1)[1].[2]() for f in files if '.' in f and f.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS}

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Arsplit

Bsplit

Cupper

Dlower

Attempts:

3 left

💡 Hint

Common Mistakes

Using split instead of rsplit may cause wrong splits.

Using upper instead of lower causes mismatch with allowed extensions.

Use rsplit to split from the right and lower to normalize extension case.

5fill in blank

hard

Fill all three blanks to define a Flask route that accepts file uploads and validates allowed types.

Flask

@app.route('/upload', methods=[[1]])
def upload():
    file = request.files.get('file')
    if file and allowed_file(file.[2]):
        filename = secure_filename(file.filename)
        file.save(os.path.join(app.config['UPLOAD_FOLDER'], [3]))
        return 'File uploaded successfully'
    return 'Invalid file type', 400

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A'POST'

Bfilename

D'GET'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'GET' instead of 'POST' for upload route.

Using wrong attribute instead of file.filename.

Confusing variable names for saving the file.

The route must accept POST requests. The filename attribute is accessed as file.filename. The variable filename is used to save the file.