Why file operations matter in web apps in Flask - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a file for reading in a Flask app.

Flask

with open('data.txt', '[1]') as file:
    content = file.read()

Drag options to blanks, or click blank then click option'

Aa

Bw

Cr

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' which opens the file for writing and erases content.

Using 'a' which opens the file for appending.

The mode 'r' opens the file for reading, which is needed to read content.

2fill in blank

medium

Complete the code to save uploaded file content in a Flask route.

Flask

file = request.files['file']
file.save('[1]')

Drag options to blanks, or click blank then click option'

Afile.filename

B'uploads/' + file.filename

C'/tmp/'

D'static/'

Attempts:

3 left

💡 Hint

Common Mistakes

Saving directly as file.filename without a folder may cause permission issues.

Saving to 'static/' is not recommended for uploads.

Files should be saved in a folder like 'uploads/' combined with the original filename.

3fill in blank

hard

Fix the error in the code to read a file safely in Flask.

Flask

try:
    with open('[1]', 'r') as f:
        data = f.read()
except FileNotFoundError:
    data = ''

Drag options to blanks, or click blank then click option'

Auploads/data.txt

Bdata.txt

C/uploads/data.txt

Dstatic/data.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using just 'data.txt' without folder causes FileNotFoundError.

Using absolute paths like '/uploads/data.txt' may not work on all systems.

The file path must include the folder where files are saved, like 'uploads/data.txt'.

4fill in blank

hard

Fill both blanks to check if a file exists before reading it in Flask.

Flask

import os

if os.path.[1]('uploads/data.txt'):
    with open('uploads/data.txt', '[2]') as f:
        content = f.read()

Drag options to blanks, or click blank then click option'

Aexists

Bisfile

Cr

Dw

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' mode will overwrite the file instead of reading.

Using os.path.isfile also works but here 'exists' is expected.

Use os.path.exists to check if the file exists, and 'r' mode to read it.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps filenames to their sizes in Flask.

Flask

import os

file_sizes = [1]: os.path.getsize(f'uploads/[2]') for [3] in os.listdir('uploads') if os.path.isfile(f'uploads/[2]')

Drag options to blanks, or click blank then click option'

A{f

Bf

Dfile

Attempts:

3 left

💡 Hint

Common Mistakes

Not using curly braces to start the dictionary.

Using inconsistent variable names inside the comprehension.

The dictionary comprehension uses 'f' as the loop variable, 'f' for formatting filenames, and starts with '{f' to create the dict.