Logging configuration in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the logging module in a Flask app.

Flask

import [1]

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

Asys

Bflask

Cos

Dlogging

Attempts:

3 left

💡 Hint

Common Mistakes

Importing 'sys' instead of 'logging'.

Importing 'os' which is unrelated to logging.

Importing 'flask' instead of the logging module.

The logging module is used to configure logging in Python applications, including Flask.

2fill in blank

medium

Complete the code to set the logging level to DEBUG in a Flask app.

Flask

logging.basicConfig(level=[1])

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

Alogging.DEBUG

Blogging.WARNING

Clogging.ERROR

Dlogging.INFO

Attempts:

3 left

💡 Hint

Common Mistakes

Using logging.ERROR which only shows errors.

Using logging.WARNING which misses debug info.

Using logging.INFO which is less detailed than DEBUG.

Setting the level to logging.DEBUG enables detailed debug messages in the logs.

3fill in blank

hard

Fix the error in the code to get the Flask app logger and set its level to INFO.

Flask

app_logger = app.[1]
app_logger.setLevel(logging.INFO)

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

Alog

Blogger

Clogging

Dloglevel

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'log' which does not exist on the app object.

Using 'logging' which is the module, not the attribute.

Using 'loglevel' which is not a valid attribute.

The Flask app's logger is accessed via app.logger.

4fill in blank

hard

Fill both blanks to configure a file handler for logging to 'app.log' with level WARNING.

Flask

file_handler = logging.FileHandler('[1]')
file_handler.setLevel(logging.[2])

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

Aapp.log

Berror.log

CWARNING

DDEBUG

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'error.log' instead of 'app.log'.

Setting level to 'DEBUG' which is too verbose for this handler.

The file handler writes logs to 'app.log' and is set to capture warnings and above.

5fill in blank

hard

Fill all three blanks to add the file handler to the Flask app logger and set a formatter.

Flask

formatter = logging.Formatter('[1]')
file_handler.setFormatter(formatter)
app.logger.[2](file_handler)

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

A%(asctime)s - %(levelname)s - %(message)s

BaddHandler

Cadd_handler

DsetHandler

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'add_handler' or 'setHandler' which are incorrect method names.

Using a wrong format string that misses key log info.

The formatter defines the log message format. The file handler is added to the app logger using addHandler.

Practice

1. What is the main purpose of configuring logging in a Flask application?

easy

A. To speed up the app's response time

B. To record app events and errors for debugging and monitoring

C. To automatically fix bugs in the code

D. To change the app's user interface colors

Solution

1. Step 1: Understand logging purpose

   Logging helps track what happens inside the app, especially errors and events.

2. Step 2: Match purpose to options

   Only To record app events and errors for debugging and monitoring describes recording events and errors for debugging and monitoring.

3. Final Answer:

   To record app events and errors for debugging and monitoring -> Option B

4. Quick Check:

   Logging = record events/errors [OK]

Hint: Logging records events and errors to help debugging [OK]

Common Mistakes:

• Thinking logging speeds up the app
• Believing logging fixes bugs automatically
• Confusing logging with UI changes

2. Which of the following is the correct way to set the logging level to DEBUG using logging.basicConfig in Flask?

easy

A. logging.basicConfig(level='DEBUG')

B. logging.basicConfig(DEBUG)

C. logging.basicConfig(loglevel=logging.DEBUG)

D. logging.basicConfig(level=logging.DEBUG)

Solution

1. Step 1: Recall logging.basicConfig syntax

   The correct syntax requires the keyword argument 'level' with a logging constant like logging.DEBUG.

2. Step 2: Check each option

   logging.basicConfig(level=logging.DEBUG) uses level=logging.DEBUG correctly. logging.basicConfig(DEBUG) misses 'level='. logging.basicConfig(level='DEBUG') uses a string instead of logging.DEBUG constant. logging.basicConfig(loglevel=logging.DEBUG) uses wrong keyword 'loglevel'.

3. Final Answer:

   logging.basicConfig(level=logging.DEBUG) -> Option D

4. Quick Check:

   Use level=logging.DEBUG [OK]

Hint: Use level=logging.DEBUG, not just DEBUG or strings [OK]

Common Mistakes:

• Omitting 'level=' keyword
• Passing level as string instead of logging constant
• Using wrong keyword like 'loglevel'

3. Given this Flask code snippet, what will be the output in the console?

import logging
from flask import Flask
app = Flask(__name__)
logging.basicConfig(level=logging.INFO)

@app.route('/')
def home():
    app.logger.debug('Debug message')
    app.logger.info('Info message')
    return 'Hello!'

if __name__ == '__main__':
    app.run()

medium

A. Only 'Debug message' will appear

B. Both 'Debug message' and 'Info message' will appear

C. Only 'Info message' will appear in the console

D. No messages will appear because logging is not configured

Solution

1. Step 1: Check logging level set

   logging.basicConfig(level=logging.INFO) means only INFO and higher levels show, DEBUG is lower and ignored.

2. Step 2: Analyze logged messages

   app.logger.debug('Debug message') is below INFO, so ignored. app.logger.info('Info message') is at INFO level, so it appears.

3. Final Answer:

   Only 'Info message' will appear in the console -> Option C

4. Quick Check:

   Level INFO hides DEBUG [OK]

Hint: INFO level shows info and above, hides debug [OK]

Common Mistakes:

• Assuming debug messages always show
• Confusing logging levels order
• Forgetting to set logging level

4. You wrote this code to configure logging in Flask but no logs appear in the console:

import logging
from flask import Flask
app = Flask(__name__)

logging.basicConfig(format='%(levelname)s:%(message)s')

@app.route('/')
def home():
    app.logger.warning('Warning message')
    return 'Hi'

What is the likely problem?

medium

A. Logging level is not set, defaults to WARNING but basicConfig called too late

B. Format string is incorrect and causes errors

C. app.logger.warning is not a valid method

D. Flask app must be run with debug=True to see logs

Solution

1. Step 1: Understand logging.basicConfig behavior

   basicConfig only works if no logging configured before. Flask may configure logging before this call.

2. Step 2: Identify timing issue

   Calling basicConfig after Flask app creation may not set level or format properly, so logs don't appear.

3. Final Answer:

   Logging level is not set, defaults to WARNING but basicConfig called too late -> Option A

4. Quick Check:

   Call basicConfig before app creation [OK]

Hint: Call basicConfig before creating Flask app [OK]

Common Mistakes:

• Setting format but not level
• Calling basicConfig after app creation
• Thinking debug=True controls logging output

5. You want to log messages to a file named app.log with level WARNING or higher and a custom format showing time, level, and message. Which code snippet correctly configures this in Flask?

hard

A. logging.basicConfig(filename='app.log', level=logging.WARNING, format='%(asctime)s %(levelname)s %(message)s')

B. logging.basicConfig(file='app.log', level='WARNING', format='%(time)s %(level)s %(msg)s')

C. logging.basicConfig(filename='app.log', level='WARNING', format='%(asctime)s %(levelname)s %(message)s')

D. logging.basicConfig(filename='app.log', level=logging.WARNING, format='%(time)s %(level)s %(message)s')

Solution

1. Step 1: Check filename argument

   Correct argument is 'filename', not 'file'. Options B is wrong.

2. Step 2: Check level argument type

   Level must be logging.WARNING constant, not string. Options B and C use string, wrong.

3. Step 3: Check format string placeholders

   Correct placeholders are %(asctime)s, %(levelname)s, %(message)s. Options A and B use wrong placeholders.

4. Final Answer:

   logging.basicConfig(filename='app.log', level=logging.WARNING, format='%(asctime)s %(levelname)s %(message)s') -> Option A

5. Quick Check:

   Use filename, logging.WARNING, correct format placeholders [OK]

Hint: Use filename=, logging.WARNING, and correct format keys [OK]

Common Mistakes:

• Using 'file' instead of 'filename'
• Passing level as string instead of logging constant
• Wrong format placeholders like %(time)s